After taking a recent look at a Java decompiler, I decided to look again at the Java obfuscator market. I was going to put together a little list of Java obfuscators, but the people at ProGuard have already done that work for me.
So, here's a link to their list of Java obfuscators, which includes a simple tabular comparison of each obfuscator.
I am currently working with the ProGuard obfuscator, and have also used yGuard. I hope to have a post here within the next few weeks about the pros and cons of each Java obfuscator tool.