http://dict.leo.org/ende?lp=ende&lang=de&searchLoc=0&cmpType=relaxed&sectHdr=on&spellToler=&search=doch http://dict.leo.org/ende?lp=ende&lang=de&searchLoc=0&cmpType=relaxed&sectHdr=on&spellToler=&search=aber Does this help?

I couldn't get to kragi's links, but let me try.

'Aber' is closer to the normal meaning of 'but''in English. Er hat Hunger, aber ich habe keinen Hunger. "doch'' can be used several ways. Often it means "but yes", "on the contrary". Hast du Katzen nicht gern? ... Doch! ich habe sie sehr gern. It can also be used to emphasize something being stated. Ich habe Katzen doch sehr gern.

Sorry for the bad links. Look at http://www.leo.org, then "Deutsch Englisch" and then type the word you're looking for.