AtomicGamer's Wasteland Enhancement Guide

The guys at AtomicGamer have given quite a few Fallout 3 mods a spin, and have put together a two-page "Wasteland Enhancement Guide" that spotlights their favorites. Let's go with their gameplay text:
Martigen's Mutant Mod F3 - This one will change the way you play Fallout 3 immensely. Most world-spawned monsters, including most Super Mutants, will now spawn two to three times as many at once, and even more with the "Increased Increased" optional add-on. It generally makes the game harder for both stealth- and action-oriented players, but it also adds some variety by equipping your enemies with new stuff and even adding new monster skins so that they look different from one to the next. There might even be a few totally new monsters kicking around.

Free Play after MQ - Don't feel like waiting until Bethesda's third add-on pack is released to be able to keep playing after finishing the game? Just install this and you'll have that option. I wouldn't be surprised if any post-main quest saves break once that DLC is released, though, so you might think about a character restart between now and April if you use this one.

Balance Mods - So far I haven't found any overall balance mods I've been happy with. Most of them make the game more difficult, which is fine, but they also add things like the need to eat or sleep which make fast travel or waiting around an annoyance. Some give weight to chems and stimpaks (or even ammo!) which will weigh you down immensely. None of the ones I've seen so far have in-game configuration options, so the more configurable (and therefore tolerable) ones require you to read through a Readme file and turn on and off each element of the mod separately in your mod manager. Hopefully further down the road we'll see some better choices.