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.
clipper caliper clapper calliper gloppier gulper gulpier galloper
lipper flipper slipper clipper flopper slippier caliper flappier slapper gloppier clapper calliper floppier loppier lopper lippier lapper slippery flapper sloppier