Is it possible to update from 2.1 to 2.3? I've got a galaxy s device and want to update it to latest android releace. I'd like to skip the 2.2 update and just do the 2.3 update. Is it possible?
It's perfectly possible to skip Android versions, but 2.3 has not been released for the Galaxy S.  See When will my phone get the Android 2.3 update (Gingerbread)?

You could try a custom ROM, however; check out XDA's SGS Development forum to find one.