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.
triple triply tripoli drippily troopial troupial tropaeola droopily
triple ripple hirple carpale cripple grapple gripple purple triply
trip tripe trippy drip drippy tarp trap trop trope atrip strip stripe stripy