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.
crap crape crappy carp crop crappie grape cripe croup crepe carpi grapy creep crepy grapey grappa crepey croupe croupy creepy creepie croppie gorp grip gripe gripy grope group kreep
rap wrap bewrap frap crap rewrap trap