I had intended to make this an extensive list, but alas, real life calls. I'll edit after the holidays and hopefully make this a worthwhile compilation.
Game Play Gibberlings 3 Tweak Pack - Sort of an Ease-of-Use and rebalancer for Icewind Dale.
Auril's Bane - Tweaks, new items, and original quests.
BGII NPCs In Icewind Dale - Introduces the 15 (plus others) NPCs from BG2 into the game, complete with portraits and soundsets.
Sorcerer's Place - Directory of useful Icewind Dale mods and tweaks.
Tioma's Ease of Use for Icewind Icewind Dale Improvements - Even more tweaks and balances for the game.
Portraits Gibberlings 3 Portrait Packs Auril's Bane Portraits - A compilition of portraits from games and other media.