No, not that kind of Marathon!
The networks are quite aware that people look for things to do on their holiday's off, and it appears that there is an interest in television marathons on Labor Day! According to PerezHilton.com, many of the top cable networks will be airing marathons on Monday. If you are planning on doing the couch potato thing you have a few options:
CSI on Spike TV
Scrubs on TV Land
The Closer on TNT
Beverly Hills 90210 on SOAPNet
America's Next Top Model (Season 10) on MTV
And if you need more than just a Monday marathon, VH1 Classic will air 80 Hours of the '80s starting Friday!