There are so many mods you can do to the Xbox that the mind boggles. For me I'm holding out for the X-Ecuter II chip which should be out within 2 weeks. Once I have that I'll change the original ata/33 cable to an ata/100 to speed things up and change the 8gig HDD (some models have 10gig).
Then comes the fun part... MAME, DVD-X and Linux awaits...