PSGw is a Skype-to-SIP and SIP-to-Skype gateway. I spent a little time this morning, setting it up on a Linux box and getting it to talk to Asterisk. While the configuration is pretty straight-forward, I did have to guess at one thing (declaring context) that wasn't in the provided notes.
Overall, the calls to/from Skype are of marginal quality. They're intelligable but there's enough jitter in them to be highly annoying.
I've put my PSGw notes in the wiki if anyone else wants to try it out.