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.
tripper trippier trapper dripper drippier dropper trooper trouper dorper draper torpor drapery droopier
gripper dripper ripper tripper crappier trippier crupper wrapper trapper drippier rapper reappear riper frippery griper gripier grippier preppier cropper crapper dropper chirper
trippy trip drippy tripe atrip strip stripe stripy