First mod that you should have, regardless of anything else you install is [url="http://www.gibberlings3.net/bg2fixpack/"]G3 Fixpack[/url] it fixes more buggs than i thought its possible *POST* official patch
As for the mods. There are many NPC mods, few that come to mind (and that i recommend) are : [url="http://www.shsforums.net/index.php?automodule=downloads&showfile=33"]Tashia[/url] the good Sorceress who romanced a Bhaalspawn before, [url="http://weidu.org/valen.html"]Valen[/url] THE evil character mod for now, chaotic evil vampir assassin who will make some decisions for you, and turn you into persona non-grata in many, many places.
[url="http://www.gilalion.com/saerilethmod.htm"]Saerileth[/url] young paladin of Tyr, who was sent by her god to find you. True force of good.
[url="http://www.gibberlings3.net/amber/"]Amber[/url]the fiery thiefling rogue with tongue sharper even than her weapon..
And many, many more including Fade, Tyris Flare, Ninde... (yes, there seem to be more FEMALE NPC mods released fully completed)
If you want some additional content in BG2 there is [url="http://www.pocketplane.net/mambo/index.php?option=com_content&task=blogcategory&id=177&Itemid=121"]Assassinations[/url]mod, that allows you to become a ruthless killer, clearing the streets of both poor and rich, harpers and paladins.
If.. You want to face tougher enemies (but tougher thanks to their script, not cheese) there is [url="http://www.gibberlings3.net/scsii/"]Sword Coast Stratagems 2[/url], a well made tactical mod
..and if you wish to change some game mechanics.. We have [url="http://www.gibberlings3.net/spell_rev/"]Spell Revisions[/url] that alter many spells both cleric and mage ones... And [url="http://www.gibberlings3.net/bg2tweaks/"]BG2 Tweaks[/url], that alter everything else [SIZE="4"](tip : Install Fixpack as first, then everything else, then SCSII, and as last Tweaks)[/size]
There ARE ofcourse dozens of other mods worth try, but those here are ones from the top shelf.
Other than SCS2 from tactical shelf there is Ascension that changes ToB battles into more challenging. (cheesy)
Improved Anvil that changes almost everything in BG2, but is the cheesiest mod released so far.
[url="http://www.gamebanshee.com/forums/baldurs-gate-ii-shadows-of-amn-9/guide-to-tactical-mods-spoilers-116063.html#post1068546"]BG2 tactical mods guide[/url]
What? You're still here? Go write a review![url="http://www.gamebanshee.com/forums/rpg-user-reviews-118/"]Here[/url]
Insane Ironman BG2 let's play! [url="http://www.bay12forums.com/smf/index.php?topic=81201.msg2140894#msg2140894"]Here[/url]