I've been playing a little with Lisp lately.  Unlike many other single-sourced languages these days (Python, Ruby, to a large extent C# and Java), Lisp comes in a myriad of flavors and implementations.  Even with the Ansi Common Lisp standard, each one has slightly different abilities.  There are a lot of things, like networking, that are not part of the standard and are done differently in each implementation.  When looking for one to play with, someone on my blog pointed me toward L#.  This looks like an interesting language and is a Lisp based on the Arc principles but built on top of the .Net CLR and its native data types.  This means that you can program lisp but have access to the entire .Net framework.  The L# front had been quiet for a while but now there is a new discussion forum for it which will hopefully spark some interest.  If you have interest in Lisp and want to use it with the .Net libraries, check out L# and the discussion group.