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.
croup croupy croupe crop group croppie groupie carp crap carpi grope cripe crepe crepy crape creep crappy creepy crepey crappie creepie gorp grip
roup group croup larrup chirrup sirup trope pyrope troop prop drupe preop droop hyperope syrup croupy grope croupe crop roupy ropy rope sirupy syrupy drop towrope trop troupe chirrupy
cru crow ecru cougar roguery scour