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.
gecko geck geek geeky jocko jack jock juco
gecko neck check wacko decoy deck sicko wreck reck pekoe pecky peck keck beck cuckoo jocko geck heck feck bucko socko deco dekko whacko shacko