Bicycle Mechanics - My bicycle brakes won't work/grip

I have a diamondback insight 3 hybrid bike. over the weekend, I took it out in some rain and My bike got dirty/wet with mud and water. I noticed my brakes did not work AT ALL. I brake, but the bike won't stop even though the pad touches the rim of the wheel. what is wrong?

When the bike is stationary, and you squeeze the brake lever hard, you should be able to lock the wheel, so that no matter how you push the bike, the wheel won't turn. The lever should still be at least an inch from the grip when the wheel is locked up.

If that's not the case, probably you need to adjust the brakes, re-clamp the cable, maybe fit new pads.

These should help you figure it out:
http://sheldonbrown.com/canti-trad.html
http://www.parktool.com/blog/repair-help/cantilever-brake-service

Those sites have pages for v brakes if you have those instead.

Many conditions contribute to the brakes working well, some enviormental and some mechanical.

If i were estimating your bike for service i start with how much lever pull is needed to have pad contact. Then how that pull feels. Then how the pads align/contact the rims. Then what condition are the pads and rims in. then after getting an idea as to the mechanical condition of the brake system we'd talk about the enviormental aspects and the rider's responsibility to change their riding behivoir when conditions lessen what ever braking capicity there is.

Your question has so many aspects that it's hard to be direct and short in the answer without seeing the bike. have you considered taking it to your LBS for their evaluation? Andy.