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.
crop croup croupy croupe crap carp croppie cripe crape grope carpi crepe crepy group creep crappy creepy crepey groupie creepie crappie gorp grip grape grapy gripe gripy kreep