I found the lack of ammo in the gameworld, especially at very low levels quite annoying. Clearing out a building actually cost you ammo, not give you more.

This mod is actually a modified version of Eduardo's More Ammo (http://fallout3nexus.com/downloads/file.php?id=2364), I just reduced the increases he made with FO3Edit, and cleaned the plugins too.

I found Eduardo's More Ammo increases a little too high and unbalancing, so I reduced them.

10mm, .32 and 5.55mm ammo is still plentyful, .308 and .44 are still much rarer, but all have been increased from vanilla levels.

Update: I was still finding there was too much ammo in the game so I have mas a new file Everso Slightly More Ammo. It doubles the ammount of common ammo like 10mm, 5.56mm, .32, energy cells, but doesn't touch .308 or .44 rounds any more.

There are 3 files:
Slightly More Ammo.esp - adds more rounds, energy cells, missiles, etc
Everso Slightly More Ammo.esp - increases common ammo and cells, but not rare ammo like .308 and .44 has been cleaned with FO3Edit.
Slightly More Ammo (explosives).esp - adds twice as many grenades and mines (this is the minimum increas allowed)

For best results I strongly recommend using Wrye Flash (http://fallout3nexus.com/downloads/file.php?id=11336), taggin it {{BASH: Relev}} and merging it into your Bashed Patch.
For Load order use BOSS (http://www.tesnexus.com/downloads/file.php?id=20516). Find the latest FO3 masterlist here: http://code.google.com/p/better-oblivion-sorting-software/updates/list