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.
croupy croup croupe crop group crepy creepy crappy crepey groupie croppie carp crap grope cripe crepe crape grapy carpi gripy creep grapey gripey grippy crappie creepie
croupy roupy ropey ropy roup croup croupe group sirupy syrupy droopy troupe chirrupy
cru crow ecru cougar roguery scour