Nubdial or dialer one in the market.
The nice thing about Dialer One is that it can display your call log right above the dialer. The nice thing about Nubdial is the way it highlights your search results. I go back and forth between them -- they're definitely worth checking out.
I use NubDial purely for aesthetic reasons.

It integrates into the OEM look of the Droid.
At least you can still access regular contacts/call log via the menu button, but I would much prefer if the call log and contacts were in tabs like the stock dialer for the droid.
Too bad you can use it to completely replace the dialer app.