http://www.appaday.tv reviews the VNC Lite app for iPhone, Ipod touch, and iPad.
Mocha VNC provides access to a VNC Server. Using your iPhone or iPad, you can connect to a Windows PC or Mac OS X and see the files, programs, and resources exactly as you would if you were sitting at your desk, just on a smaller screen.

LITE VERSION:
Compared to the Lite version the full version has:
- Another cool key board
- Extra keys as ALT,CTRL, Option and the Apple key
- Support for right mouse button, hover and mouse wheel
- Macro support
- Ctrl+alt+del key. Needed if using Win 200x as a VNC Server
Get it from the app store here.