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.
dirk drek dark dork dreck drouk drake dorky darky darkie drecky darkey derrick dreg trek drug drag turk daric duroc tarok track traik trick trike troak trock troke truck
birk irk kirk quirk mirk dirk chirk shirk