Anyone else tried out https://www.cloudflare.com ? I've been a part of the private beta, and I have to say, it works very well. It basically adds a layer between your web server and the user, caching your website (well- parts of it), and intercepting and challenging any user agents it sees as a threat.
It was started by the Honey pot folks, and has both free basic and paid pro plans.
It has reduced the load on my Linode to almost nothing, which for a person like me who is not the best at server config is very helpful.
Anyway- two thumbs up from me- highly recommended.