Reverse phone lookups?

[Jason Barnett]

What websites do people use to do reverse phone lookups? I.e. someone gives you a phone number and the website can tell you the address associated with that phone number.

Obviously there are a lot of problems with certain types of numbers (cell phones and blocked numbers often produce no results). So I'm looking for free sites or pay sites that can produce results for these hard-to-locate phone numbers. I'm tired of not being able to verify all of these phone numbers lol.