Here are a few themes I like for Mac Terminal. If you're not a fan of Terminal itself, I also suggest looking into iTerm2.

My Favorite Themes

• Peppermint
• Piperita
• Monokai
• SMYCK
• Solarized

My Favorite iTerm2 Themes

• Peppermint

One Step Beyond

If you want to create your own custom theme, then I suggest you visit Terminal.sexy. Terminal sexy is a web app that lets you create, preview and share your themes.