Learn the 'harmonic scale' and the limitations of building progressions from the Cycle of Fifths. See especially Chapter 6. You can read chapters 1 to 6 free online.
This is a list of links to songwriting and composition resources on the net.
Creative Chord Progressions
http://www.squidoo.com/disharmony
Feel free to add your own links that you come across. Cognitone will review this list from time to time and add selected links to the "official" link list on our homepage: http://www.cognitone.com/support/links.stml
Mixed bag of links on composition:
A Jazz Improvisation Primer (German translation)
Learn the 'harmonic scale' and the limitations of building progressions from the Cycle of Fifths. See especially Chapter 6. You can read chapters 1 to 6 free online.