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.
guaco guaiac guck quack cacao quacky cuckoo gag cog gowk coca coke gook coco coky caca gogo gawk cook cock kagu gaga quag
guaco bucko juco cacao quack taco wacko whacko shacko
guaco guaiac guck quack quacky