SHTUP--installs the high-resolution textures and fixes for in-game objects that allow the game to make the most from the large modern displays. It adds much detail to the things that surround you in the game, from potted plants, through monitor screens, up to every single graffiti.
Four Hundred--another important texture pack. It makes the game's scenery look crisp and sharp by applying high-res textures to walls, floors, doors and whatnot, while remaining quite faithful to the original mood.
Vurt's Space--for those of you who love stargazing. This mod applies nice high-res texture to the in-game windows, so you can admire the ominous beauty of the Tau Ceti system while looking through them.
SHMUP--music update! It provides the game with better quality files of the original soundtrack, so you can admire the excellent work of the composer Eric Brosius, just as he'd wanted you to hear it.
All of the above improve on the game's various aspects but don't affect the gameplay. If you don't mind to stray somewhat from the game's original feeling and concepts, there are also some mods allowing you to change such things as weapons, enemies, and AI behaviour:
ADaoB--this is a modification offering fixes to some of the original game's quirks and re-balances the gameplay. Please note that you will have to start a new game after installing, as the changes are severe enough to make the game incompatible with earlier savegames.
Rebirth--enemy models modification. It replaces the original AI models with their more detailed counterparts, that make use of modern systems' power.