If you use Verizon Wireless and their online service, My Account, you can use Backup Assistant for free!

As a My Account member, Back-Up Protection will let you automatically retain a copy of your saved phone numbers to a secure web site, so they’re always available if you lose or upgrade your phone.

I love that it updates everyday at my specified time. When it was time to upgrade my phone, it was painless.

Get it. Use it.

Note: If you have more than one phone number for a contact, it doesn’t retain the default number you use for your contacts. Extremely minor, though.