So I find myself with a crowded desk: one laptop, a mouse for the laptop, a keyboard, mouse, and two LCDs for my desktop. It's getting crowded, and it gets annoying to switch between different keyboards.
Worse, I do all my Thunderbird email just off the laptop (though I use GMail on either or both). That's a problem when I need to copy text from the desktop to the laptop so I can mail it.
Solution: Synergy -- an open source tool that links my computers together.
Synergy allows me to use my desktop keyboard and mouse on both systems. The mouse travels off the left side of my desktop screen onto the right side of my laptop screen. Focus follows mouse, at least in terms of system-to-system, so I can type on one system (say, the desktop), move the cursor over to the laptop, and type into the active window there (without clicking). Synergy even updates window decorations.
Better yet ... Synergy supports cut-and-paste of text between the two systems. So I can copy text out of my browser on the desktop and paste it into compose window on the laptop. I had thought about using a KVM switch at one time, and this kicks its ass! In fact, had I discovered this a few weeks ago, I might not have bought a mouse for the laptop.
Not an issue for me, but it's also cross-platform. It supports Windows, Linux and (with some problems) Mac OS X.