Need a rhyming dictionary? (chances are that you do, even if you don’t realize it yet.)
Then check out the Rhyme Zone.
This is incredibly useful and extremely easy to use, and can also be handy with the thesaurus application. I found it an incredibly valuable resource when I was writing a villanelle poem about Abraham Lincoln (don’t ask. The only thing I got from that experience is that I’m obviously not very good at writing villanelles.)