[image of Reflector]
A co-worker introduced me to this little utility for .Net. Reflector is a nice assembly browser that includes a disassembler, call graph and callee graphs. Very nice! I can point it at my assemblies. Then with a few clicks I can drill down into disassembled source for system libraries and third-party libraries that I am calling. Reflector also has some plugins for DB browsing and other stuff.
Reflector is available from http://www.aisto.com/roeder/dotnet/.