If you were one of the lucky ones that got your hands on the PS3 already and are looking to make it into a lean mean DVR machine Gizmodo has the how to for you. You will need to be sure that you have enough space on the internal HDD of your PS3 to begin.

Then Gizmodo says you will need a USB keyboard and mouse and their handy dandy how to that walks you through the rest of the steps. Once complete you can even use the PS3 as a web server.
It’s interesting that you can do this with a PS3, but it seems odd to me to use a gaming console as a DVR. I guess at the price Sony asks for the macked out PS3 they wanted to give potential buyers all the incentive they could to pick up a PS3. Buy your own PS3 here.