If you've been looking for a new VOIP app for Android, you need to take a look at Line2. Forged form the bowels of Toktumi, Line2 is in the same vein as Google Voice in that you get a new phone number. But unlike Google Voice, it will place calls over Wifi or 3G/4G data when available, or over the regular network when it's not.
You get a 30-day trial, and it's $9.95 a month after that for unlimited calling and texting in the U.S. and Canada. It's still a little green, certified only for the Droid, Droid 2 and Droid Incredible, and it's a no-go on Galaxy S phones running Android 2.1 (that's all of us here in the States), and glitchy on the Evo 4G. But with the free 30-day trial, we'll give it a go.