What do I do next in Fallout?

Right now, I'm at Tenpenny tower, made Megaton explode into Oblivion, I did another quest to kill some ghouls in a station. What, where do I go now?

either walk around till you find some or try this

http://fallout.wikia.com/wiki/Fallout_3_quests

maybe the first quest for the main quest line

or you could maybe do stealing indepencence in rivet city

you missed out tho not doing wasteland survival guide

This is why Fallout 3 is so great. You have more than one option, you can just walking around and find new locations, talk to people, get quest, kill whole societies, etc... Follow the main quest line which will lead you to major cities where you'll find more things to do, blah blah blah, or just walking around looking for the best armor and guns and kill every one and everything. All of these options can be really fun. And if you're done will all the quest that Fallout comes with I highly recommend the all 3 DLC, they all have their own unique story, and force you to adapt to their world since 2/3 times they take all of your gear away and give you completely new DLC weapons. Have fun.

P.S. Wiki will help you find where all the main quest (Being the ones that give you achievement, and generally the most fun) start, where to go, what to do, up to the end. It also tells you where all the strongest weapons and gear are. I believe it's called the Vault. ... Here's a link.http://fallout.wikia.com/wiki/Fallout_Wiki

Go find Oasis. It's one of the coolest places I've ever seen in a game.

Or go work on the main story. It's a lot of fun.