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.
splay supply sappily soapily sepal spail spale spall speel spell spiel spile spill spoil spool speil supple
play splay byplay replay ply loopily peppily happily papula pepla pula pily haply roupily ropily cupola sappily ripely dopily whoopla choppily hiply soapily paly plea reapply ploy hoopla reply apply ripply deeply copula cupula poly nippily supply deploy duopoly cheaply shapely