Pulpgrinder Rhyme Finder looks for rhymes and near-rhymes in a word list of over 130,000 words. Rhymes are sorted according to strength.
Optionally, you can enter a syllable/stress pattern and Rhyme Finder will do its best to find a word that matches. Use / for a stressed syllable, and * for an unstressed one. As with pronunciation, this can vary in different English dialects, but in most cases it should provide a reasonable approximation.
