I dropped CableTV quite awhile ago, but honestly, with a HTPC (Home Theatre PC) I don't miss a thing.
Now that all the major content providers are pushing their TV on the web its much easier for folks to walk away from the CableTV bill, and still get "TV". Nevermind HD OTA (High Definition Over-the-Air) antennas...I'm talking just web here. There's a truckload of content out there right now. Free.
If you have an HTPC, and/or have dropped cable and own a computer with an internet connection (preferably high speed), you should be familiar with some basic apps:
XBMC is probably one of the oldest and well known apps for HTPC it would be ashame if this were the first time you were hearing of it. Free, open source, and it'll play just about anything. Great UI for use with a TV, including old TV's, or new TV's. Playing HD, SD and just about everything. File formats galore.
ImgBurn and DVD Decrypter are probably some of the easiest and most reliable ways to rip any existing content owned on disc to the hard drive. Add this to your library, and suddently a gigantic DVD/HDDVD/BluRay shelf full of discs becomes one neat little library of 1's and 0's on your HTPC hard drive. Imagine your entire movie library at your fingers...
So that's it, basic 4 apps for HTPC. And you drop CableTV. Do it!