My most recent project is a HTPC, or as I like to call it: Zigvo. I built my first HTPC almost 10 years ago and ran it with myHTPC software (which later became Meedio and then sold-out to Yahoo!). Later, it graduated to Freevo with a short stint using MythTV.
Since then, I have given up on the constant tweaking and toying with the open-source and Linux-based software. I have found that Windows Media Center works very well and is widely supported with a lot of great free plug-ins. It has also greatly improved my WAF.