LifeHacker: "Lifehacker came up with a good way to get free Google Voice calls on your desktop with Sipgate, but Sipgate seems to have run out of free numbers, rending that method broken (for now). VoxOx can do something similar.
Here's the deal: When you sign up for VoxOx you get 1 free number that you can use to hook in to your Google Voice with. You also get free incoming calls (which means incoming AND outgoing calls with Google Voice, cause GV always is the one to call your phone), incoming texts and incoming faxes. Outgoing calls (if you're dialing straight from the VoxOx client), outgoing texts and outgoing faxes cost money. So while you can get incoming texts to your VoxOx account, responding using that IM window is a bad idea, since you get charged about a penny per text."