The 2nd DLC for Fallout 3 has been released yesterday.
http://fallout.wikia.com/wiki/The_Pitt
I've already downloaded it, but haven't started the quest yet. I also have the 1st DLC, which i haven't started to play either.
I thought i'd wait until the 3rd part is released next month, and then play them all, while leveling up to level 30.
However, i've started playing the game again now. Thought i would keep exploring a little, and eventually started to collect all the bobble heads. Only to find out that i've missed one bobblehead during the main story... it's in raven rock apparently, and if you miss it during that mission, it's gone forever. I started looking for savegames before that mission, but no luck, they are all overwritten or deleted.
Now call me crazy, but i already had collected more than half of them... so i've decided to actually start a new game again. Total playtime on the previous savegame was about 110 hours...
At least i'll have one month until the 3rd DLC gets released. Should be enough to reach those 110 hours again!
On a sidenote: I thought it would be tedious to do it all again, but so far i'm about six hours into the game, and i enjoy it as if it would be the first time... such an awesome game!