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.
group groupie croup grope croupe croupy grip crop gorp gripe gripy grape grapy grippe grippy grapey grappa gripey croppie carp crap
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