Generate Unique User Name Online is a free tool based on an unique algorithm which allows you to generate an endless number of random user names that would be suitable for use on the Web. Really don't get the point of this one to be honest. Sure, the name you want might be taken, especially if your name is John Smith, but it's not THAT hard to come up with other ideas, surely?
To be honest, the names that this thing does come up with are pretty pants. Bozigqu, Choodiye, Maaobyp, Lirtimya? Be easier to let a dyslexic monkey attack your keyboard for 5 seconds.