Over the last few days I’ve been getting into using screen. To over-simplify, the idea is sort of like tabbed browsing for the command line (except that you don’t actually see the tabs).
It has a long man page and lots of options, but mostly I’ve just got the hang of ctrl-a c (for new command-line “tab”) and ctrl-a n (for switching between the various “tabs”).
I put “tab” in quotes because it’s not really tabs, but it’s enough like tabs so that it’s an easy way to describe it.
If you find yourself opening lots of Terminal windows, then it’s worth looking at screen.
Another option is iTerm, which is an actual tabbed terminal app for OS X. (My only wish for iTerm is tabs that are more like the tabs in Safari or Transmit or PathFinder, rather than just what appears to be a standard NSTabView. In other words, the tabs could take up less screen real estate.)