I don’t purchase a lot of apps for my iPad, but Air Video was one of the few. Air Video streams video to your iPad, iPhone, iPod Touch from a server that runs on Windows or OS X. The thing that impressed me so much was how well the remote access works. I can stream all of my videos from my server at home to my iPad wherever I am as long as I have a WiFi connection. No loops to jump through, SSH to setup, or ports to forward. Performance was flawless even though I was running the server from a virtual machine with a network share to stream my videos, on an iSpot WiFi pipe!. It just flat out works.
Air Video - $2.99
Great how-to on setting everything up via How-To Geek