Skype 2.5 adds major Mac features to VOIP client
According to MacsimumNews:
It features the ability to send SMS messages to any mobile phone in the world. Also, Mac users can now use Skype to hold conference calls with up to nine other people. Calls can be made to Skype contacts for free and to landlines and mobiles for a small fee, via SkypeOut. There’s also a new birthday reminder feature.
Another major new (if hidden) feature is the ability to have high-quality (640*480) video calls with others - a boon if you're toting a MacBook/Pro with a built-in iSight camera.
It's a bit of a hack to enable (normal video calls are capped at 320*240) but according to Skype Garage the experimental feature can be had by adding two simple lines to a file called config.xml, which enables the high-resolution goodness.
Take that iChat!
If you want to try it out and have a Mac-based tip, my Skype handle is jason_ogrady.