I've tried a few solutions for using multiple computers (mostly one MacBook plus one or two Windows machines) simultaneously and I've currently landed on http://synergy-project.org/ as the One for Me.
It's very good. It's pretty seamless (last year less so, this years seems perfect) : put 3 machines next to each other, move your mouse across the 3 screens, and control and type into whichever computer has mouse focus. It's particularly a good solution when some of your machine are laptops and you want to use the laptop screens.
Alternatives I've tried:
- VNC and remote desktop style solutions have worked best for me when I have multiple monitors on a single machine. The irritation is when your local monitor isn't as big as you want for the remote machine and you end up with a scrolling window. The itch that remote desktop solutions don't scratch though is when some of your machines are laptops, and then you want to use the laptop screen. Of the various options, TeamViewer and MS Remote Desktop seem the fastest; I haven't yet seen a fast solution for Mac.
- When I don't need a gui, I find
sshor similar is really good. Even a modest monitor easily has room for multiple console windows. A reminder perhaps that guis are not always the bee's knees.