Here's a 'blog entry where someone seems to have basically ruined their DSLR by cleaning the sensor with a liquid cleaner.
One of the problems with digital SLR cameras is that dust can accumulate on the sensor, since you're swapping out the lens from time to time.
There are a few solutions... Olympus' E-300 is self-cleaning. Other DSLR manufacturers instruct you to use an air blower to gently blow the dust off. Another solution has you using a statically-charged brush to get the dust off.
And then there are some companies manufacturing a liquid solution, where you wipe some kind of solvent across the sensor. The problem, however, is that the 'sensor' you're cleaning is actually a piece of glass which is sealed on top of the actual sensor, and if that seal is broken, then the solvent could wick between the sensor and the glass.
Which is what happened in that 'blog link above.
I use an air blower. It's made by Giotto and looks like a rocket ship. It's cute. :-)