It's a Mod, Mod, Mod, Mod World
(Yes, we know, this corny reference dates us!)
Over the last decade the BG modding community has created some excellent mods for BG1 and BG2. The majority of mods have been written for BG2. But a large number of mods are compatible with the Baldur's Gate Trilogy (BGT) and Big World mod platforms that uses the ToB engine to play BG1. And mods that revise spells or classes, for example, modify BG1 when using BGT.
Over time we'll build up a comprehensive directory of mods on this page, both for the original game (typically using Tutu or BGT) and BG:EE. For now you may refer to the modding communities' own respective websites to peruse their mod lists.
Below are the modding communities (and lone modders) that we're aware of. If you know of any the we have overlooked please post here.
Mods for BG:EE
List of Mods Available for BG:EE
Baldur's Gate Mods
Pocket Plane Group
JOG's Baldur's Gate Corner - Wild Mage Additions