My only computer's the laptop, a 17" Macbook Pro. It's probably a bit too big—next computer I get I'll drop down to 15"—but it's not a computer I anticipate getting rid of any time soon. It's a bit grungy, but it works beautifully.
OS X for the main operating system. Nothing on the menubar but battery life, Dropbox, FuzzyClock, and Alarm Clock.app. Dock's hidden by default and has nothing on it but the programs I open myself. No stacks.
I constantly run SterCleanDesk, which moves anything I put on the desktop to a storage folder, Google Quick Search Box, which is my launcher, and Fresh, which has two compartments, one for recently modified applications and one for storage. In storage I also keep my most-used folders, so when I need to navigate I just open up Fresh. I use the basic Apple programs for most things (iTunes, Safari, TextEdit, Mail), iWork for making pretty documents, Scrivener for screenplays, Coda for programming, Transmission for torrents, Skype for chatting, and iSquint and Max for file conversion.)
It's a pretty dream set-up. It stays completely out of my way and it does everything I want with minimal interference. I've tried adding to-do lists to my routine—I have a hard-on for Things—but I find that I really don't have a reason to prod myself into productivity. Now I go by my own routine and it works perfectly.