Pay attention to names in the real world. Write down interesting names you come across in newspapers articles, in the telephone book, hear on the radio, etc. I’ve created character names adapted from names I’ve come across in graveyards or on hotel registry lists. If you’re really stuck, go for the baby name books. They’re full of names. That’s what they’re for.
Interestingly, Baby Names.com has some notes for writers on picking good character names.