Zafiro and DMZ (for talking it through), William, Iansounet (for that tough love on the outside and the gooey marshmellow fudge on the inside!), jay, cmorgan, Andrea, other people that I forget at this very moment, people that wrote readmes, people that cleaned up after me when I cried myself to sleep, etc.
With help from all of you here, I've compiled a list of modifications which are commonly used to boost the gaming experience. This isn't finished and will soon be updated with links to documentation for whatever install you might be doing. I'll provide sufficient detail so that, in case you're new to the mod business, we can help. Remember to read the posts below.
This can include core system changes, gameplay mechanics, content, areas, soundsets, portraits, etc
Baldur's Gate Modifications:
Baldur's Gate Tutu/EasyTutu:http://www.pocketplane.net/tutu http://usoutpost31.com/easytutu/
Tutu (manual installation) is a program which copies parts of the game archives from Baldur's Gate and Baldur's Gate 2 (ToB not required but useful) and supplies a separate installation. This installation is essentially Baldur's Gate and it's content, but operating under the updated engine powering Baldur's Gate 2.
EasyTutu is an installer which creates a preset recommended version of Tutu, without all the fuss.
Features include added races, classes, kits (sub classes, I guess) and 800 x 600 pixel resolution (from the original one of 640 x 480). The GUI (interface) which the gamer uses to navigate the game will be of Baldur's Gate 2, however, another mod can be used to change this to the original interface of Baldur's Gate.
Baldur's Gate Trilogy:http://www.spellholdstudios.net/ie/bgt/
Trilogy is another common installation process which converts the engine of Baldur's Gate to Baldur's Gate 2. It copies game archives from Baldur's Gate and places them in your Baldur's Gate 2 directory, rather than making an entiely separate installation. A player can seamlessly play through Baldur's Gate and it's expansions with Trilogy, rather than stopping and reimporting their character for Baldur's Gate 2.
1PP (Spellhold Studios):http://www.shsforums.net/forum/159-1pp/
One Pixel Productions is set of modifications which restores the paperdolls (inventory characters) and avatars of Player Characters and NPCs in BG2 to that of their BG counterparts, as well as edit inventory icons.
This can be applied to a BGTrilogy or Tutu installation. If the latter, it can then be applied to your Baldur's Gate 2 installation as well. A very popular mod, considering the quality of paperdolls and avatars in BG2 is considerably less.
Baldur's Gate 2 Tweaks (G3):http://www.gibberlings3.net/bg2tweaks/index.php
This popular modification allows you to selectively modify game rules, cosmetics and applies various fixes.
BG1 NPC Project (G3):http://www.gibberlings3.net/bg1npc/index.php
This is divided into three packs.
BG NPC Banter, which applies large amounts of interaction between NPCs party members and the Player Character, including friendships and romances.
BG NPC Music, which applies suitible music backings to these interactions (as opposed to spoken voice, which could not be arranged).
BG NPC Portrait, which is a minor cosmetic altering component. It gives you the opportunity to replace some NPC portraits with fresh ones designed by the community members.
Icewind Dale Modifications:
This modification allows infinity engine games to be played at higher resolutions for supporting monitors, meaning standard sizes of 640 x 480 or 800 x 600 can be increased to fit modern screens. However, it should be noted that title menus, pages and User Interfaces remain scaled and so become furthur squeezed as the resolution is brought up.