The chord chart that Colmes provided a link to is a good place to start.
Certain types of music typically follow a certain chord progression.
For example, folk music typically follows a I, IV, V pattern. For the key of C your chords for a tune might be C, F, G. The same tune in the key of G would use G,C,D.
Lyrics will have natural breaks where you change pitch. Play with the chord changes at those points.
Try taking a young childrens book and putting chords to it. Sound like an odd exercise? The words to childrens books normally rhyme or have a beat to them. They have repeating phrases, and are short. You don't have to worry about writing lyrics, just working on a chord progression pattern that fits the tempo/beat of the story. Then you get some fun wacky songs out of the deal too.