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.
griper gripier gripper grippier groper grouper grapery grapier carper crapper cropper crupper creeper crepier crappier creepier croupier corpora
riper griper ropery roupier wrapper frippery harper carper ropier crapper creeper crepier gripper raper larruper proper sirupier dorper drapery drippier dropper tripper trooper warper chirpier groper croupier roper gripier reaper rapper rapier crappier creepier cropper reappear crupper grapier ripper grapery grippier grouper preppier puerpera syrupier draper dripper droopier trapper trippier trouper chirper sharper
grip gripe gripey grippe grippy gripy cripe gorp grape grapey grappa grapy grope