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.
trippier tripper drippier dripper trapper dropper trooper trouper droopier dorper draper torpor drapery
crappier trippier grippier preppier drippier reappear crapper trapper rapper droopier gripier ropier dripper sirupier creepier wrapper croupier ripper roupier crupper grapier frippery gripper rapier syrupier dropper crepier tripper cropper chirpier
trippy trip drippy tripe atrip strip stripe stripy