I have the Fallout 3 "Game of The Year" edition, and have played it through all levels up to Level 30, and I've reached a point where all it seems there is left to do is gather Sensor Modules, Cameras and Super Mutant Blood samples for the brotherhood at the citadel.

Is there an actual end to the game, or is this it?
Am I missing something?

Nope, that's it. Broken Steel removed the definite ending from Fallout 3. All there is for you to do now is the stuff you mentioned before, as well as killing off respawning Raiders and other enemies, and exploring areas on the map that you haven't gotten to yet.

I was wondering the same thing because I have not gotten to level 30 yet. Thanks for clearing it up for me!