This is a drop-in replacement for java.util.Hashtable, written by Dr. Cliff Click and donated to public domain. It is lock-free and still multi-threaded safe. It can scale linearly to 768 CPUs.
The repository was in sourceforge and seems to be not as well-known as it should be. So I copied it here in the hope of letting more java developers use it.
javac build.java java build all
You can also check out README.cliffc for more instructions.
There's also a video by Dr. Cliff Click talking about the lib: http://www.youtube.com/watch?v=k5FltpgKcVk