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.
sugar sugary saggar seggar soucar square saguaro scar scour sacra scaur scare sucre cigar scary saker scurry squire sacker scarry sucker secure scarey sowcar soaker sagger saggier soggier suckier scry
sugar cougar gar sugary soucar augur square seggar saggar muggar gaur guar quare agar beggar eggar vagary hegari jaggary jaguar maugre megara cigar beggary saguaro chukar