Updated June 28, 2017: AnyWho reverse lookup changed. Only works for white pages, not cell #s.
These are a few of my favorite phone directory search sources.
If you find these useful, check out the rest of: www.jsrsys.com
Yahoo! People Search
Reverse Telephone Search
AnyWho has chosen to make their reverse search function unavailable from other web sites.
Please click above to directly access their reverse search page.
The AnyWho Directory Service provides on-line access to U.S. residential telephone listings. It includes more than 90 million entries for all 50 state plus Washington, D.C. Entries can be added or updated quickly and easily.