For Clojure, there's an interesting startup (TheDeadline) that developed using Clojure and Google App Engine. They have a good ppt on Slideshare and an interview on InfoQ.
For a good discussion on deploying Clojure with GAE:
http://news.ycombinator.com/item?id=1239788
As far as I know, Clojure has a few web development libraries.
Compojure
Ring
Conjure
Hope this answers some of your questions =) (I'm just starting out too..)
Best,
Ryan
