So i've completed the main quest line (including broken steel) and all the DLC's except Point Lookout...between the two areas (because from what I could tell, there wasn't much to the Pitt outside the fairly short main quest line) where are the coolest places/most interesting things to do? To be honest, i really haven't seen most of the world outside of what you have to do to complete the main quests and don't know where to start

also...try not to spoil too much please

Just walk around, set a random point in the Wasteland and walk there, chances are you'll find several cool things on the way.

What's even cooler, is to set a map marker at a random spot downtown. Sometimes, if you place it right, you will find that the route it presents to you will include places and tunnels you've never been down before.