WatchFire has released a white paper on HTTP Request Smuggling - a new type of attack that targets multi-layer HTTP stacks (proxies, caches, firewalls).

What is HTTP Request Smuggling?

HTTP Request Smuggling (HRS) is a new hacking technique that targets HTTP devices.

I found a site that has some good security tips for web developers. It mentions one type of attack that doesn't get much attention - called Cross Site Request Forgery (CSRF).