- Caffeine: Keep your Mac from sleeping.
- Carbon Emacs (F): Well, this is cross-platform. And you know, I can't live without it. Plus, Carbon Emacs has some nifty additions. Check it out!
- Disk Inventory X (F): Shows graphically the size of files sitting in your drives. A quick way to find those hard disk eaters you have but are not sure exactly where.
- Growl: Let your applications talk to you.
- Fugu: thin MacOS FTP client.
- Nethack: For the work breaks!
- Platypus: Turn your bash script into a nice application.
- Reduce: Algebraic manipulator, among others. Cross-platform.
- TabletDraw (S): 35$, but it is the best tablet drawing program I have come across, at least for this price. The shareware version has all options, but limited undo capabilities and just 2 layers.
- Think: Keep your attention in just one application.
- sLife (F): Easy time tracking for the Mac. But it seems to make Nethack crash :/
- Quicksilver (F): The application launcher to beat all other application launchers. Pressing CMD-Space followed by i and enter to launch iTunes saves a lot of trackpad moving.
There are a few Mac applications I use so often, I couldn't live without them. And most of them are free, or really kind shareware.