I haven't cleaned my yoga mat yet either and I've had it for years, I figure I'm the only one using it, can't be that germy ...
As for Yoga DVDs my DD and I love this one:
It's not a beginner tape but you just go at your own pace, but it would help to know basic yoga moves and terminology... Although having said this, my DD does it all the time now and she had never done any type of yoga before...