Mac OSX Terminal Tip 2 (Transparent Background)
Wednesday, September 12th, 2007 -- By ETdefaults write com.apple.Terminal TerminalOpaqueness 0.8
You can change the last number from 0 to 1.0, I found 0.8 to be nice. If you want to freak out, try 0.
Oh changing this has the added benefit (cost?) of making the background of the dock transparent. I like it
