I second this. When I wrote my first frustum cull method it opened up so many other possibilities. After clipping, I would say look into writing a quadtree (2d)

I second this. When I wrote my first frustum cull method it opened up so many other possibilities. After clipping, I would say look into writing a quadtree (2d) followed up by an octree (3d). Even though quadtree's are confined to a single plane they are quite useful even in 3d games. I can recommend the game programming gems series. I don't know what number they are up to now, I had the first three and they were a huge asset in learning all these techniques and more.