Twitter has a very nice touch in their signup process that I’ve not seen elsewhere. As you type in your preferred user name, Twitter tells you stroke by stroke whether that name is available. For example, D, DO, and DOT are not available, but DOTT is. I kept typing till I got to DOTTIEH, which is (or was – now it’s mine) available.
For once I didn’t have to submit myriad possible names one after the other until I could find a unique one through trial and error! This is a very thoughtful product design detail that makes things better for the user. I hope other web services adopt Twitter’s approach.