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.
purply purple preapply preppily propel propyl prepill propyla propylaea
purply sharply triply carpal chirpily droopily replay preppily preapply croupily creepily carpel foreplay drippily airplay reapply roupily ropily ripply ripely reply purple hirple
perp prep prepay preppie preppy prop