MissingRemote published a HTPC software guide, you can read it over here.
Each one of these has their pros and cons. If you are using Mac OSX, you don't have many choices beyond Front Row and Plex (below). If you're using Linux, honestly you're probably not reading this guide due to limited options as well--MythTV (below as well). So that leaves Windows users . This is at least 90% of you out there, and most likely what everyone reading this is interested in. Let's take a look at some HTPC software programs and cover some of their pros and cons. By no means is this full in-depth, but should be a good starting point.