A few days ago, a very interesting thread about fictional user data was posted to programming.reddit.com. As I happened to be needing large amounts of fictional user data myself about the same time, I took some inspiration from that thread and wrote a simple "Dummy Data Generator." The code is now up on GitHub for anybody who wants to use it.
This generator will make realistic looking, but totally fake, names, addresses (US and Canada), email addresses, phone numbers, etc. If you want to load some social networking software - or something similar - up with a large number of accounts, maybe to do some performance testing, this might just be useful to you.