I have the Game Of The Year Edition Fallout 3 and i swear i have found every Location that has a map icon. But im not really sure. Know how many locations there are?

There are 162 locations without the DLC and 163 locations with the regulator perk. DLC adds 10 more locations to the Capital Wasteland and the DLC alone has 225 locations.

Use this link for more info.

http://fallout.wikia.com/wiki/Fallout_3_locations

Yeah like Smokin Aces said, there is a lot on the Map. I haven't visited them all and I have been playing Fallout 3 since it came out.