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.
koppa kappa kop koppie kapa copay cuppa cowpea cop kep kip coop cope copy coup goop keep kepi
koppa poppa chuppah hoppy huppah copay cuppa kappa loppy opah nappa poppy pupa soppy dopa choppy chuppa shoppe