I use iTeleport for remote desktop functions. Very nice VNC client. It has a small app you can install on your Mac, if you choose, that will enable dynamic IP address forwarding integrated into a Gmail account for those who have dynamic IP addresses for their desktop computers (most ISP do not assign static IP addresses).
I've used the iPhone/iPod version for a year or so with good luck (formerly called Jaadu VNC). Only downside is it's a bit pricey, but worth it IMHO.
If you want to stream video from your Mac, look at Air Video. Remote desktop apps are not ideal for fast-moving video or games.