Here is the Application Manager version of SP3 for Navisworks Manage 2016:
http://download.autodesk.com/SWDLDDLM/Updates/NAVMAN/2016/Autodesk_Navisworks_2016_SP3_ML_Manage_64bit.msp

Other links:

 Autodesk_Navisworks_2016_Service_Pack_3_Multilingual_Freedom_64bit.msp (msp – 101,280KB)
 Autodesk_Navisworks_2016_Service_Pack_3_Multilingual_Manage_64bit.msp (msp – 139,380KB)
 Autodesk_Navisworks_2016_Service_Pack_3_Multilingual_Simulate_64bit.msp (msp – 139,380KB)

 
Readme

 Autodesk Navisworks 2016 Service Pack 3 Feature readme.pdf (pdf – 259Kb)
 Autodesk Navisworks 2016 Service Pack 3 Installation readme.pdf (pdf – 120Kb)

Autodesk page:
Navisworks 2016 Service Pack 3 | Navisworks Products | Autodesk Knowledge Network

Download links:
Installer
Readme
Release Notes

As can be seen in release notes below, most of these are “Improves stability…” fixes.

Platform
 Annotation
  Improves stability when creating dimensions.*
 Family
  Improves stability when editing families*.
 IFC
  Improves placement of the site on Open IFC if the site is located away from the origin, or rotated.
 Schedules
  Improves data integrity of a schedule instance on a sheet with the schedule view.*
  Corrects the name of the Default Structural Area Reinforcement Schedule.*
 Selection
  Improves stability when attempting to use the Selection Box tool in Reveal Constraints mode.*
 Upgrade
  Improves stability when upgrading a model containing corrupt families.*
  Improves stability when upgrading projects which may have some corruption.*
  Improves stability when opening or upgrading a Revit 2015 project which contains stairs.*
 Views
  Corrects an issue causing view filter names to be automatically appended when workshared models are synced.
  Improves stability when editing selection sets in a workshared model.*
  Improves data integrity of Project Address for upgraded projects.*
  Improves stability when selecting a viewport with the Select by ID tool.*
  Improves stability when canceling out of the view templates dialog.*
 Worksets
  Improves stability when deleting an element which may have an invalid ID.*
 Worksharing
  Improves stability when using the Options dialog to log into A360 from a workshared central file.*

Architecture
 Wall
  Improves stability when editing stacked wall types*.
  Improves stability when cutting rooms to the clipboard.*
  Improves stability when clicking Edit Preview in the wall structure dialog.*
  Improves stability when editing the structure of walls.*

MEP
 Annotation
  Improves placement fidelity with wire tags when upgrading a project.*
 Electrical
  Improves stability when no panel schedule template is assigned as the default.*
 Fabrication
  Improves connection consistency of taps.
 Groups
  Improves visual fidelity of lighting fixtures within a copied group after the original group is modified.*
 Mechanical
  Improves stability when using Mechanical Settings.*
 Pipe
  Improves stability when upgrading a project that contains user-created pipe types.*

Structure
 Analytical Model
  Improves stability when opening a project which contains a Structural Isolated Foundation with an invalid analytical model defined as a column.*  
 Families
  Improves stability when placing a slanted column or a beam based on a Generic Model Line Based family.*  
  Improves stability after reloading an annotation symbol family used as a symbolic representation of brace elements on plan views.*  
 Scheduling
  Improves stability when selecting a viewer element associated with Graphical Column Schedule.*  

API
  Improves stability when using Dynamo and the function: Select Divided Surface Families.*  
  Improves stability when DimensionSegment ValueOverride API is called when the dimension value was not overridden.*
  Improves error handling with element’s methods/properties.*
  Improves consistency of UIApplication.PostCommand for pre-selection.*
  Improves error handling with ElementCategoryFilter.*
  Improves stability when editing families which use external resources for keynotes.*
  Adds a validator to the Rotate Tap API to guard against creating invalid models.
  Improves error handling with UIDocument.PromptToPlaceViewOnSheet() function.
  Improves consistency of the RebarContainer element.*

Most of these are bug fixes, and some BIM360 Glue integration performance improvements. Details and direct links below:
Autodesk Navisworks 2016 Service pack 2 delivers user experience and stability improvements to the Autodesk BIM 360 integration. Service pack 2 also addresses problems identified in other parts of Autodesk Navisworks 2016. Service Pack 2 also includes all of the updates from Service Pack 1. Service Pack 2 can be installed on either the original version or the Service Pack 1 version of Autodesk Navisworks 2016.

Autodesk_Navisworks_2016_Service_Pack_2_Multilingual_Freedom_64bit.msp (msp – 78Mb)
Autodesk_Navisworks_2016_Service_Pack_2_Multilingual_Manage_64bit.msp (msp – 101Mb)
Autodesk_Navisworks_2016_Service_Pack_2_Multilingual_Simulate_64bit.msp (msp – 101Mb)

Readme
Autodesk Navisworks 2016 Service Pack 2 Feature readme.pdf (pdf – 422Kb)
Autodesk Navisworks 2016 Service Pack 2 Installation readme.pdf (pdf – 308Kb)

From http://knowledge.autodesk.com/support/navisworks-products/downloads/caas/downloads/content/navisworks-2016-service-pack-2.html

The focus of Autodesk Navisworks 2015 Service Pack 3 is the resolution of Revit interoperability issues. Service Pack 3 does resolve issues identified in other parts of the product, we recommend you refer to the supporting documentation for the detail.

Download Navisworks 2015 SP3

Autodesk_Navisworks_2015_Service_Pack_3_Multilingual_Freedom_64bit.msp (msp – 202.29Mb)
Autodesk_Navisworks_2015_Service_Pack_3_Multilingual_Manage_64bit.msp (msp – 269.44Mb)
Autodesk_Navisworks_2015_Service_Pack_3_Multilingual_Simulate_64bit.msp (msp – 269.45Mb)

Readme
Navisworks 2015 Features (English)
Navisworks 2015 Installation (English)

via
http://knowledge.autodesk.com/support/navisworks-products/downloads/caas/downloads/content/autodesk-navisworks-2015-service-pack-3.html

EDIT: Subtle change – dragged window selections and markup are now filled blue in colour

Remember to update your exporter if necessary:
2015: NavisworksExporters2015.exe

Now available in Application Manager, direct links:

Autodesk_Navisworks_2015_Service_Pack_2_Multilingual_Freedom_64bit.msp (msp – 201Mb)
Autodesk_Navisworks_2015_Service_Pack_2_Multilingual_Manage_64bit.msp (msp – 265Mb)
Autodesk_Navisworks_2015_Service_Pack_2_Multilingual_Simulate_64bit.msp (msp – 265Mb)


Service Pack 2 resolves an issue opening and appending multiple files in a single operation. The Service Pack also resolves issues identified in our Point Cloud support, Autodesk Rendering, Quantification, Clash Detective, and interoperability.

Readme and install links:

Main Autodesk page:
Navisworks 2015 Service Pack 2 | Navisworks Products | Autodesk Knowledge Network

EDIT: Updated Links

Note – the Enhancements List shows a lot of improvements to stability, so this Update comes highly recommended.

Revit OneBox / RVT (for Suites) Update 2

Revit 2013 UR2 (32-bit) (exe – 59699Kb)
Revit 2013 UR2 (64-bit) (exe – 83079Kb)
Readme (select language version):

English (htm – 32Kb)

Enhancements Documentation (select language version):

English (pdf – 206Kb)

via
Autodesk – Design & Creation Suites Support – Revit 2013 Update Release 2

Revit Architecture 2013 Update 2

Revit Architecture 2013 UR2 (32-bit) (exe – 59699Kb)
Revit Architecture 2013 UR2 (64-bit) (exe – 83079Kb)
Readme (select language version):

English (htm – 32Kb)

Enhancements Documentation (select language version):

English (pdf – 202Kb)

via
Autodesk – Autodesk Revit Architecture Services & Support – Revit Architecture 2013 Update Release 2

Revit Structure 2013 Update 2

Revit Structure 2013 UR2 (32-bit) (exe – 59699Kb)
Revit Structure 2013 UR2 (64-bit) (exe – 83079Kb)
Readme (select language version):

English (htm – 34Kb)

Enhancements Documentation (select language version):

English (pdf – 203Kb)

via
Autodesk – Design & Creation Suites Support – Revit Structure 2013 Update Release 2

Revit MEP 2013 Update 2

Revit MEP 2013 UR2 (32-bit) (exe – 59699Kb)
Revit MEP 2013 UR2 (64-bit) (exe – 83079Kb)
Readme (select language version):

English (htm – 32Kb)

Enhancements Documentation (select language version):

English (pdf – 203Kb)

via
Autodesk – Autodesk Revit MEP Services & Support – Revit MEP 2013 Update Release 2

Older post:
It doesn’t seem to be ‘official’ yet, but the Update 2 download links are live at:

Revit Architecture 2013 Update 2
http://updatesdl.autodesk.com/updates/files/rac2013ur2.exe

Revit Structure 2013 Update 2
http://updatesdl.autodesk.com/updates/files/rst2013ur2.exe

Revit MEP 2013 Update 2
http://updatesdl.autodesk.com/updates/files/rme2013ur2.exe

Revit OneBox / RVT (for Suites) Update 2
http://updatesdl.autodesk.com/updates/files/rvt2013ur2.exe

For Revit OneBox (Building Design Suite version), the link should also eventually appear at:
http://usa.autodesk.com/adsk/servlet/ps/dl/index?siteID=123112&id=2334435&linkID=16831210#section21
when it is available (I will also update this post when there is an official suite version Update 2 link)

Heads-up via:
Revit OpEd: Watch for Web Update 2