There are a number of threads on the best vanilla with minor fixes kind of mods. What are the best user-created mods for BG1 and BG2 that are beyond the vanilla?

I'm mostly looking for good writing, as I think that's the critical component, but any contribution will be helpful.

For BG1, I recommend the NPC project: http://www.gibberlings3.net/bg1npc/

Also these NPC mods, if you're using Tutu:

Gavin: http://www.gibberlings3.net/gavin/

Finch: http://www.pocketplane.net/mambo/index.php?option=com_content&task=blogcategory&id=134&Itemid=94

For BG2:

Banter pack: http://www.pocketplane.net/mambo/index.php?option=com_content&task=blogcategory&id=95&Itemid=78

NPC flirt pack: http://www.pocketplane.net/mambo/index.php?option=com_content&task=blogcategory&id=104&Itemid=81

Romantic Encounters: http://www.gibberlings3.net/romanticencounters/

If you install NPC mods, the Cropssmod banter Pack: http://www.gibberlings3.net/crossmod/

Some popular NPC mods:

Xan: http://www.pocketplane.net/mambo/index.php?option=com_content&task=blogcategory&id=164&Itemid=113

Angelo: http://www.gibberlings3.net/angelo/

Kivan: http://www.gibberlings3.net/kivan/

Gavin: http://www.gibberlings3.net/gavin_bg2/

Edwin (adds a romance component to an existing NPC): http://www.spellholdstudios.net/ie/edwin

Sarah (includes a lesbian romance): http://www.gibberlings3.net/sarah/

Amber: http://www.gibberlings3.net/amber/

de'Arnise Romance (adds a romance to an existing NPC): http://www.pocketplane.net/mambo/index.php?option=com_content&task=blogcategory&id=119&Itemid=118

Warning: do not install the romance cheat components of the BG2 Tweak Pack if you want to install NPC mods. Unless you install the Crossmod Banter Pack, you can run multiple romances by default. Always read the readme files before installation to make sure you have the correct installation order. If you install the mods in the wrong order, you might mess up your game.