There is a pretty decent freeware product, if you can get past the 'bling' of the website where you download it, can do wonders to inspire new lyrics and rhyming strategies.

I used it extensively this past February, when I wrote 7 songs, with at least 3 verses each, choruses and bridge sections.

http://www.bryantmcgill.com/Free_Rhyming_Dictionary/

I used to use rhymezone.com, but this thing has more flexibility.