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.
crappy crap crappie grapy crepy crape grapey creepy grippy crepey grappa croupy croppie carp crop creep crepe cripe croup grape carpi gripy croupe gripey grippe creepie
crappy frappe harpy grapey grappa grapy grippy preppy drapey drippy trippy sharpy