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.
sloper sloppier slapper sleeper slipper sleepier slippery slippier
looper eloper walloper galloper blooper sloper loper clapper leaper caliper flapper floppier helper pulper lippier flipper lipper loopier flappier gulper slippery sleepier sloppier leper flopper calliper slapper slippier slipper sleeper loppier bleeper pulpier gulpier lopper gloppier lapper clipper yelper
slope slop sloppy saloop salp salpa salpae slap slip slipe slippy sloop slype aslope