Jim Calloway blogs about 3 free directory assistance numbers to program into your phone.
I’ll add at least one more: your public library’s quick reference line. It will be useful only during those hours your public library has reference hours, but in some places that’s a lot of your working hours. You could also just plug a Library per Time Zone into your phone.
My own favorite local library reference line is:
Multnomah County Library Reference: 503-988-5234 (they have an amazing, and enviable, offline quick reference collection too, though I usually phone for an address or phone number or directions, or a book title I can’t quite remember)
Some libraries now also have a text message service, for those times you can’t speak up, e.g. the Washington County (Oregon) Cooperative Library Service InfoQuest service.