Macworld has a great article listing 11 essential apps for your iPad. These are all paid apps. The one that really caught my eye is Air Video ($2.99), which lets you stream video from your Mac or PC to your iPad, iPhone, or iPod touch. It actually converts the videos on the fly to a format compatible with your device. (You need to also download the free desktop software in order to do this.) The hitch with this program is that only works with video that's not copy protected. You can also use the software to convert videos without taking advantage of live streaming.