Rhyming dictionaries can be handy, but rhyme isn't too important in itself. I think partial rhymes and a verbal echoes that aren't rhymes at all can often work just fine in songs. Metre is far more important, getting the stresses in the lines to balance with each other so it doesn't sound forced.

The fundamental thing is that a song should sound like a natural way of using language, and if there's a rhyme scheme, sound as if that's just a happy outcome that arose while you were saying what you wanted to say, not that you're saying it that way to get it rhyming. (Apart from songs where you're using rhymes for an effect, probably a funny one - Golbert and Sullivcan for example.)