Actually to each not of the major scale there is a chord dedicated. In the case of C major scale you get :

C Dm Em F G Am Bdim

or with 4th chords :

Cmaj7 Dm7 Em7 Fmaj7 G7 Am7 Bm7b5

also view http://www.guitartricks.com/tutorial.php?input=551

These are called diatonic chord progressions. Now you can start to make songs out of these chords and most songs in a major key work only with these chords. The most popular chord progression is I IV V - C F G in any variations. Other examples are :

I VI II V
I II V
I II III IV V

or you can find you ways of making combinations from those diatonic chord progressions. :)

Greetings

HP