I presented a lightning talk tonight at DotNetOxford on '10 VS Extensions You Might Have Missed' covering some perhaps lesser-known items in the Visual Studio Marketplace. All of these extensions are free, and they all provide a useful addition to what you get out of the box in Visual Studio.
UPDATE: And now you can see the whole evening's set of talks at https://www.youtube.com/playlist?list=PL4qgjzgv2UYTTCbWELKjyJrcKMz02K7DH
Customize Visual Studio Window Title
Azure DevOps Status Monitor
Trailing Space Visualizer
Warn About TODOs
Stack Trace Explorer
I hope everyone got something out of this and found at least one extension that might be useful for them!