Tip: More than two tuners - Ramon Van Bruggen is a star
As you may know Media Center Edition natively supports a maximum of two tuners (well 3 if you also have an over the air HDTV card in the US)
For quite a while there have been a number of forum posts around the web (particularly on the Green Button) with walk throughs of a complex procedure to add more tuners, these have been beyond the average mortal though.
Thankfully Ramon Van Bruggen is about to change that with what like it may become the ultimate utility for adding more than one tuner. Its in early beta but is progressing very nicely.
Head on over to http://mce.ramonvanbruggen.nl for more information and to join the beta programme.