Know-How Exchange : Other

I need to come up witha list of ideas for a vanity phone number. I was using AT&T's Toll Free Number lookup to validate whether the ideas I have are already numbers in use. Is that a good way to come up with a list of valid vanity phone number options?

I am not really interested in finding out what can be spelled with the current toll free number. This is more a brainstorming exercise, but I don't want to waste a bunch of time thinking up great ideas if all of them are already taken. I've never been asked to do this type of thing so I don't know where to start.