Some tools I highly recommend …

All are free or relatively inexpensive (the ones with a license fee are well worth it).  Most are excellent learning tools as well as productivity tools.

LINQPad: I can’t say enough good things about this gem!  It’s a scratch pad for .NET applications and so much more!  The .Dump() method is fantastic!

.NET Reflector: Great way to look deep into the .NET Framework and more.

Balsamiq: I love this mock-up tool.

.NET Memory Profiler: Profile early, profile often.

ReSharper: I never go anywhere without this one!