What open source .Net utility projects or code libraries do you use? [closed]

Question

I use log4net in just about every code project. I was wondering what other generally useful code projects are available?

Answer 1

• Rhino.Mocks
• NUnit
• NHibernate
• Spring.NET
• Castle
• My own somewhat eclectic MiscUtil
• PostSharp

Answer 2

I like the C5 collection classes, from the IT University of Copenhagen:

http://www.itu.dk/research/c5/

It's one of the most well-designed libraries, of any kind, I've ever used.