[jds375]

I also recommend GeekTool. It allows for some cool customization effects. Available for free here: http://projects.tynsoe.org/en/geektool/ You can find some cool themes from devianart or other sites.

[blacksmith_tb]

It's sort of abandonware now, isn't it? There's NerdTool, which works well enough for me, but also hasn't been updated in a long time...