(Bump) This is the reason I entered the site today as well. When the phone was introduced the front cam could only be used for video calling over regular networks.
There's also VZO video chat for the Samsung Omnia which supports the front cam, but there hasn't been an update to the software for a long time. Furthermore it requires both users to have VZO chat.
In addition I found an article on how to activate the cam to function as a mirror, but not for Skype calling:http://www.pspmyspace.com/omnia/2009/01/how-to-use-the-front-camera-on-the-samsung-omnia.html
There's also the SDK on this very site which enables turning on the front cam for other uses than official network video calls.