A few things that I have found helpful as a songwriter...
Books that will help you hone your craft...
Pat Pattison: Writing Better Lyrics
Websites for Songwriters...
Objectwriting.com is a great site for developing the ability write with strong emotion and imagery. I highly recommend joining the forum and completing the object writing word of the day. You set a timer for 10 minutes and write using your senses. How do things look, feel, sound, smell, taste, etc. There is a deeper explanation on the site.
Some of my favorite songwriting videos...
Blogs that have challenged me as a writer...
Christianmusicblog.com is a great resource for people of faith who make music. It is geared toward those who write. It is full of great interviews with people who write, produce and market music.