I spent some time this week switching from bash to zsh (I really enjoy zsh - I treat it as bash with floating point arithmetic and other niceities) and making a theme for oh-my-zsh and prezto for myself. I'm not quite done, but I am pretty pleased with the results.

It differs from most themes in the following ways:

• Explicitly not having git or other version control info in the prompt (I very rarely don't know what branch I am in and when I care about the status of git, I usually care about which files are affected).
• Showing the execution time and status of the last command executed.
• Displaying a notification (on Mac OSX) if a (long running) command completes and the terminal isn't in the foreground.

First, a screenshot:

And some more detailed explanation:

• By default, the prompt is very minimalist (the current directory and a % or a # depending on the privileges of the shell). Most extra information is hidden unless it is useful.
• In the right hand prompt, the execution time of the last command is displayed. It is colored green if the command returned successfully and red otherwise.
• The number of background processes is displayed (but only if there are background processes).
• If the path to the current directory is long, it is also displayed in the right hand side.
• The user and hostname are displayed (only) if logged in over ssh.
• Since this is zsh, the right hand prompt disappears if the line is long enough.

Source is in my fork of oh-my-zsh and my fork of prezto.