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.
rigor rigour rigger regrew regrow rocker rugger reekier require rockery rockier roguery rookery rookier
rigor vigor gor goer gore gory agora vigour maigre rigour cigar
rig brig ergo frig grig prig trig trigo