Looking for a name for one of your fictional characters? Or do you simply need an alias for yourself? Zulugrid has put together a fake identity generator, useful not just for names but contact information as well, perfect for situations such as:
Signing up for paid offers (like affiliate programs that pay for leads) or those annoying free iPod pyramid schemes. If it doesn't require you to actually get something shipped to you, then a real looking fake name/address from another state can be real useful.
Pseudonym to use as your online identity to avoid companies from seeing your colorful past. If you use an "unused" name, then it will be very easy to search for everything related to yourself using Google.
Load it (or a couple) into a form filler to quickly fill out junk mail forms. Very useful if they want you to refer 5 friends or whatever.
Fake websites to promote your own website. Work at least the city/state into it somewhere and it looks like people from all over the country are raving about your *insert something cool here*. Of course, thats a lot more work than I'd be willing to do. Maybe if I generate an XML API like someone suggested, it could be done automaticall...
Sweepstakes site that is used to gather names/emails to sell. Use the fake names/addresses as the people who "win" your sweepstakes.