Hide TV Listings (htvl)
https://chrome.google.com/webstore/detail/hide-tv-listings-htvl/emahdgfobodhknccbigjmnhpgihmmjbf
It hides the channels you don't want to see, and filters you can customize.
Here is the thread regarding the extension:
http://forums.comcast.com/t5/XfinityTV-Website/Chrome-Extension-to-Hide-Channels/m-p/2309083#M35523