Ok, I want to start writing songs. I want to write songs that basically use 4 chords for the verses. I have two questions...

1. How do I change from a 4 chord progression for the verse to another 2/3/4 chord progression for the chorus. I need to know how to pick two progression that will fit together, or will all progressions fit?

2. Is there a site/page that lists ten or twenty or even all possible chord progressions. Well at least simple 3 or 4 chord progressions. And if it lists chord progressions that it "fits" with as well.

The first song I want to write is a really sad song, so I want to fit it to a 4-chord progression in a minor key, that switches to a 2-3 chord progression riff for the chorus. I need to understand the theory behind it, but a list of heaps of progressions for songwriting or something similar would be great!