Free for today only...
I like Remoter ($0.99) for working with my SmartBoard within my room - http://itunes.apple.com/us/app/remoter-remote-desktop-vnc/id3696260... (as long as you are on the same network you can control any computer from anywhere within the network as long as you know the IP address and login info for that system).
I also have LogMeIn ($29.99) - http://itunes.apple.com/us/app/logmein-ignition/id299616801?mt=8 which, while expensive is far move versitile. I can access any system I've installed Ignition on from anywhere on the web, I don't need to be on the same network. It's been great for accessing my class system from home or at a meeting.
Remoter is my daily use app. LogMeIn is my security blanket for when I'm out of the building.
SplashTop is low on my list. On the iPad the resolution is horrible and the controls, to me, are lacking.
If you want a free controller I'd go with Mocha VNC Lite. Remoter is still, in my opinion, the best available and the best use of $0.99.