iStat Pro & FreeSpace
Lastly, I like to know at any given time how much space is available on my computer. Is this strictly necessary? No, but I just like to see this information. For the OSX Dashboard, I use iStat Pro for showing system information. Along with disk information, it also shows temperatures and CPU / Memory / Network usage. It is useful and free.
Also, I use a program called FreeSpace, which puts an icon in the notification area of the task bar that shows me how much space is left on my hard drive, as well as the ability to eject any attached drives by clicking it. I do not use the drive ejecting much, but the real-time free space number is extremely useful.