I had a need to move some VB.NET code to C# today. We're still not at the point where we can just mix and match languages within an assembly, and in this case, it would be more work than I wanted to separate things out. I looked around the net, and the best code converter that I found (read: it successfully converted everything I threw at it, where others failed) was this one.
Disclaimer The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way.