I've taken a list of English words, and examined each of them to see what they sound like (using the PHP metaphone function). This page lists the most common metaphone codes, along with their words. You can also search for a word of your own, and see which words sound similar - and which ones rhyme, and which ones alliterate.
groups groupies croups gropes croupes grips gorps crops croupous gripes grapes grippes grappas croppies carps corps craps crepes cripes corpse corpus carpus crapes creeps kreeps crappies creepies
roups groups croups syrups crops corps burps ropes pyropes dropsy droops hydrops towropes troops troupes urps croupes croupous gorps props dorps liriopes drops hyperopes drupes preops hydropsy larrups trappous gropes tropes sirups turps chirrups
group groupie croup croupe croupy grope