Feeling nostalgic about Pi calculus, theorem proving and all those nice things you were used to play with back at your university time?
Jorgen Thelin gives you the chance to brush up your formal reasoning skills in association with web service security topic, by introducing project Samoa from MS Research: http://www.thearchitect.co.uk/weblog/archives/2003/11/000258.html
That page is a real gold mine of precious info, check it out.
Happy studying! 🙂