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.
kneader neater needer needier nuder nadir neuter netter natter nodder knitter nattier nettier knotter knottier gnattier niter noter nitery notary nutter niterie nittier nuttier
header deader leader beader kneader reader ladder gadder leadier lieder madder adder aider beadier fader seedier feater wadder readier reedier sadder seder beater lewder heeder eater heater raider shadier eider needier lauder ceder weedier needer loader padder lader bedder headier neater deedier wedder heder cheder redder feeder seater seeder badder tedder wader weeder cheater shader shedder