Roof Racks?
 

Does anyone know of a source for detachable roof racks? I would like the kind that clip to the gutter and have knobs thus require no tools. I occasionally need to carry a step ladder or a few 2x4's.

Many bicycle shops carry roof racks of the kind you describe. Typical brands are like the ones found at
http://www.thuleracks.com/thule/default.asp?flash=true&height=600
or
http://www.yakima.com/index.html

I used to work at a bike shop way back when and I can say that Yakima is the better of the two listed above. They don't have the rusting problems that Thule does. If its for intermittent use then you can go for the cheapest option (Sera I think).

I really wanted to warn you though that if your meticulous about your paint be very careful when mounting a roof rack. Make sure that the paint is extremely clean or you'll find that the clear coat will be dulled. Don't leave the rack on the car for extended periods of time either.

When you go to a bike shop they'll have all the sizing charts for your car as well as the types of acessories you want such as straps to hold that ladder in place. Good Luck