Restricting Command+tab options to only apps that are in the current space
control+F4.  Cycles through the applications in that Space.
 (I actually have this mapped to control+`; which I find easier to remember, being close to the cmd+`; to cycle through an application's windows.)

To change the keyboard shortcut, go to the Keyboard preferences, Keyboard Shortcuts, and Keyboard &amp; Text Input.  It's the 'Move focus to active or next window' option.

(Edit to fix the keyboard shortcuts; I didn't realise that the backtick character wasn't showing up.)