inumbr is a free online service that gives US users the ability to set up a unique phone number, have it forwarded to any number within the US and then have it set to expire without a trace when finished with it. The unique inumbr’s are never reused, and can be extended if longer terms are required. Users choose from a list of 22 area codes from major US cities like Chicago, Los Angeles and New York, select an expiry date and set a number that it should be forwarded to. When the term is up, the number is expired from the system, and never used again for any other user. If you wish to use the number at a later date, you can log into the inumbr system and reactivate it.
Interesting, how soon are they going to face the first legal issues because of "miss-use" of their service? Other then that, a good service to bookmark.