Control: You can often rent live traps from municipalities, or have animal control take care of that for you.

Deterrent: You could set up a timed or motion-activated sprinkler system. I know that you can buy pre-made units, but I'll bet if you're handy you could rig up your own. If it's tied to a light turning on you can condition the cats to scram whenever the light comes on.

Here's a link to a motion-activated ultrasonic cat repeller. No affiliation. No idea how well it works, but Lee Valley doesn't usually sell junk.
http://www.leevalley.com/US/garden/page.aspx?p=59764&cat=2,51555&ap=1