I know Java well. Which caveats and resources will help me cross to the other side (C#) as painlessly as possible.
The language syntax is vary similar, so I should only read a small reference of the C# syntax. Like a simple book (for experienced programmers) or maybe wikipedia (http://en.wikipedia.org/wiki/Comparison_of_Java_and_C_Sharp) will tell enough.
The biggest difference is the library: Asp.Net websites are totally different from java servlets.
Don't read much, just start programming!
There's a cheat-sheet from Microsoft for Java developers using C# :)
Here's a link that has syntax comparison between Java and C# (even though it's almost identical, there are a few differences).
http://www.harding.edu/fmccown/java1_5_csharp_comparison.html