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.
supply supple sappily splay soapily spell sepal spail spale spall spill spiel speil spoil spool speel spile zeppole zeppoli
reapply ripply supply apply ply ploy rappel fipple popple replay haply happily ropily roupily hiply soapily supple appel dapple deploy duopoly topple choppily nipple byplay splay hopple play pily paly loopily apple reply peppily ripely appal ripple nippily sappily poly deeply dopily tipple cheaply shapely
sup sappy soppy soup soupy supe