Erik Meijer, guru at MS Research, has recently given a talk at OSCON 2009 introducing functional programming in a funny way. Highly recommended if you have always wondered what all fuss about side effects and purity is about.
Check it out : http://blip.tv/file/2402061/
He even cite Mono around 4:30 (btw Erik, Mono has supported C# 3.0 for quite a long time now ;-) ).
To conclude, "Go purify yourself because you are all sinners" :-) .