I was just about to post about this. It would be awesome to have Skype make an app for Roku DVP. I tried to find contact info to send them an email, but haven't yet. While not everyone would adopt this would add another great functionality to our little boxes.
One of my friends just purchased a 42" HD tv but didn't feel he wanted to spend the high $AMT on the high end TVs that have skype built in....and so he merely connected his laptop via HDMI to his TV (with wireless home network) just when he wanted to skype....and its AWESOME. Anyone who skypes on laptop should try this....better camera angle, better view. nothing short of awesome. He also has a logitech 720p videocam give this a try until someone is smart enough to figure the Roku thing out!!!!!
The overhead to SEND the video in linux is just too much. I have to do quite a few kludges to get my video camera to work in linux skype. So many cameras, low memory on Roku - I just don't think it would be possible to send.
You could always use a tablet or laptop for local vid and figure out a way to transmit the remote vid to the roku... thats what I would do because if I am in a skype call I can see the person on tv that way.