This looks like an interesting way to do skype calls from a regular phone: rapidBox.
Trouble is, I do so little long-distance calling, and it's so cheap, and none of my family use skype, that I doubt I'd actually break even. Plus you need one for each phone. (Please don't comment by saying “Asterix”, ok? Gotta get some Linux boxes up and running first. And that won't start until the home renovations are long over.)