If you are a Home Theater PC fan and want your HTPC to tune those unencrypted QAM digital cable channels, one of your best options is the HDHomeRun dual QAM tuner. SiliconDust's HDHomeRun tuner has been one of my best gadget purchases to date and I'm still a happy user since the beginning of 2007. If you'd like to learn more about the HDHR tuner, check out my review of the HDHR from last March HERE.
The setup since that time has changed quite a bit (for the better) for both Snapstream's Beyond TV PVR software as well as SageTV's HTPC software.
For a nice walkthrough of the setup process for setting up the HDHR with BeyondTV check out ProjectHTPC's guide HERE
And for another how-to based on setting up the HDHR with SageTV's HTPC software check out the guide by Floppyhead.com HERE
Either way, setting up the HDHomeRun is pretty easy and is a great addition to any Home Theater PC.
You can find out purchase and more setup information for the HDHR at the SiliconDust website.