I bought a Pinnacle PCTV Dual DVB-T Pro PCI recently but would hesitate to recommend it as it was painful getting it to work properly. I had to use their beta software and drivers in the end. It's ok now but I wish I had gone for the Hauppauge Nova-T 500 (the other card I considered at the time) which other people are recommending.
I think I may have a look at MediaPortal this weekend - it looks interesting. Not heard of it before.