I was going to start a thread called "resources," but that is dangerously broad. Here, I want to focus on two things. First a post for the big one, then another post for the little one.
Writing Better Lyrics by Pat Pattison
A MUST READ for lyricists!
I was tempted to post the notes I took on this book, but the Internet theorem ("anything you can think of is almost surely already on the internet") applies. So check out:
His own page at http://members.aol.com/ptpattison/lyricpages/index.html
tips under "lyric tips"
and about the book under "books"
A reprint of chapter 4 at
http://www.lyricist.com/bookshop/ch4.html
Look inside the book at Amazon
http://www.amazon.com/Writing-Better-Lyrics-Pat-Pattison/dp/1582970645
Second, to get those non-cliche rhymes, this has proved useful:
http://www.analogx.com/CONTENTS/download/audio/rhyme.htm
It's a 100,000-word rhyming dictionary, and freeware to boot.
It's for the PC, so you Mac guys are out of luck. (What do I know - there's probably an iRhyme applet there already.)