EDIT 14/02/2019 - Replaying Fallout 3 on PS3, made some amendments to the guide. Feels weird editing a post from 10 years ago, but hope someone still finds it useful!
These are in order of discovery. You MUST find the first 19 before the space walk, you cannot get back to the lower level afterwards. Pretty sure the last six need to be done before completing the DLC, needs confirming.
1. #14: After escaping your cell, head left. It's in the far right room.
2. #22: As above.
3. #15: As above.
4. #3: In the room after the first red health arch, on your left.
5. #1: As above.
6. #12: As above.
7. #5: On one of the stasis chambers in the room where you get the spacesuit.
8. #6: As above.
9. #7: As above.
10. #8: As above.
11. #2: In the Cryo labs, in the southwestern corner of the rectanglular shaped building to the south.
12. #11: In the Cryo labs, the second northmost room before you go through to the Cryo storage (Right of the door).
13. #17: As above but left of the door.
14. #25: Cryo storage, room at the southern tip.
15. #16: In the bottom left corner of the Cryo storage, on the lower level.
16. #4: After teleporting back to the Cryo labs, head directly south and use the door release switch. Hop down to the lower level to grab the recording.
17. #13: Cargo hold, in the research lab in front of the lunar module in the left-most room.
18. #21: In the next room, near some robot Giddyup Buttercup horses (the 6 horses, not the dozen or so down the stairs).
19. #19: Go to the maintenance level, then after meeting up with Sally and making your way through the scrap, you will end up in a large room with a healing arch on your left and an alien behind an energy shield in front of you. After killing the aliens, look to the right of the door you entered through.
THE PREVIOUS 19 LOGS MUST BE COLLECTED BEFORE THE SPACEWALK, YOU CANNOT RETURN TO THESE AREAS. Take a second to double-check the Notes section of your Pip-Boy to make sure you have all 19 so far.
20. #24: After the space walk, enter the weapons lab. It's in the control room in the south in a slightly lowered section.
21. #20: When you enter the experimentation lab, head right until you get into a room with two big torture chair looking things. Do a 180 and look at the wall to find it.
22. #10: In the experimentation lab, in the final room along with the generator.
23. #9: Beside the operating tables in the experimentation lab with the abominations.
24. #18: On the upper level of the bio research control room.
25. #23: In the living quarters cafeteria, after the Death Ray (Thanks to THEeskEMO)