I recently discovered the most excellent tmux:

tmux is a terminal multiplexer: it enables a number of terminals (or windows), each running a separate program, to be created, accessed, and controlled from a single screen. tmux may be detached from a screen and continue running in the background, then later reattached.

I dabbled with screen previously but abandon it because it didn't actually improve my workflow much over Terminal.app's tabs. tmux, however, supports horizontal and vertical splits! This allows me to work the same way on terminal that I do in vim.

I ripped some pieces from various configs around the net: