My favorite is the Expert Name Finder. It lets you select a whole bunch of different parameters to narrow down your name choices.
Here's an example using my current work-in-progress. For the main character, I wanted a boy's name that was fairly common in the US, and one that suggested intelligence and youth. I also didn't want it to start with the letters S, H, or L, since I have character names starting with each of those letters already.
Here's what my search looked like:
And here are my results:
This gives me lots of names to choose from. I especially like Aaron, Quinn, and Terrence for this character.
With these tools, naming characters is a snap!