damage could occur...just like using a magnifying glass to focus the sun's rays to burn things.... the lens of the camera is also focusing the suns rays...onto the sensor.
that said, with a dslr you should be fine as the sensor is exposed to the sun for a very short period of time. but with a normal p&s where you can compose with the lcd... you'd better be quick in composing.
a more serious issue is eye damage from composing through the viewfinder. i've heard ppl using the DOF button to help dim things... but even then, becareful!
Be careful also. Don't use colour negatives or slides. Use ONLY true silver halide B&W negatives (not the C-41 process type) because the black area is silver which is able to fully absorb/reflect the invisible IR/UV rays which are more damagging. Visible light forms only a very small band of the spectrum.
Hm i had a friend who used a D50.There was once we pointed the camera at the evening sun and thereafter all his pics had a permanent red line.He brought it to NSC and they had to replace the sensor:sweat: