Since the PS3 trophy patch was released, I went ahead and created another game and am playing through a second time. A few tips to speed things along if you're hunting the trophies/achievements:
SPOILERS WARNING! This is optimal for a trophy run on a second play through. I would encourage playing the game as intended the first time through and enjoy the excellence of Fallout 3!
1) Before doing anything you should grab a list of the
20 bobblehead locations. Some of them, such as the ones in Megaton, Vault 101, and Ravens Rock could be lost forever depending on choices you make/your progress in the game.
2) When you Escape Vault 101 at the beginning of the game, change your tag skills to Lockpick, Speech, and Science to maximize your opportunities to get to 50 successful on each. As you level up, max out speech as soon as you can, then science, and lockpick last. If you are about to screw up a lockpick or hack attempt, back out and then try again. You can save a lot of bobbypins on lockpicks this way if you're close to running out. Early in the game, you may want to save upon entering any major locations and speaking to quest-giving NPCs, that way you can retry the speech challenges you fail.
3) Play the game as close to neutral as you can, and don't do anything with the Power of the Atom quest in Megaton. Do not even talk to Burke. At some point early in the game, you should also walk to the Tenpenny Tower location to get it on your map to speed things up with fast travel later, but do not start any quests or engage the Ghouls. This way, at level 7, when you are about 300 XP away from leveling up, you can save your game. Now, go into Megaton, talk to Burke, follow through with blowing up Megaton so that you level up to 8 as evil for the achievement. Then reload from the earlier save, go outside the front gate of Megaton and give Nicky Purified Waters until you're good (should take only three or four), now you can go back in, disarm the bomb to save Megaton for a quick level up to 8 as good for that achievement. Reload from your save again, and on the third time just continue about your game, killing creatures to get the Neutral achievement at level 8. If you don't do anything at either Megaton or Tenpenny Tower, those options will be there for you throughout the game, so you can repeat this at levels 13/14, and 19/20 for those awards. With the locations already open on your map and fast travel, you can hammer out all three using one gamesave in under 30 minutes. Do that for all three and you can knock out all 9 achievements off one play through and without too much extra work. That'll be ALOT faster than playing the complete game three different times.
4) The fastest way through, IMHO, is to do only things essential to the main story
up to Little Lamplight/the Finding the Garden of Eden quest. This will open many sections of your map for fast travel later, so the optional quests can be completed much more quickly. You'll also have found The Citadel and will be able to wear Power Armor to make things a bit easier later on with all the side quests. Another benefit, you'll be able to talk to Zimmer in the Rivet City lab and kick off the Replicated Man quest early on, so there is a good chance you can take the easy path out and finish the Replicated Man quest when you find the woman from 'the Railroad' in Grayditch while doing the Those! quest.