You can meet and talk to a legendary four - "The Beatles". Famous musicians by the will of fate found themselves on Faerun. It's just an unusual meeting and couple of dialogs, no new stuff, spells or quests.
The current version is v1

For original BG1 (with or without TotSC), the mod adds a friendship track and the BG1NPC project romance for Ajantis. The original BG1NPC project romance was slightly altered to adjust to the restrictions of the BG1 engine, although overall the content stayed the same. For Tutu and BGT, the mod adds a friendship track for Ajantis. Contentwise, the friendship mod is meant as an addition to the BG1NPC project, but technically it can be installed and played without the BG1NPC project.
The current version is v1

Adds several new banters, representing hundreds of new lines of dialogue, to BG2. No special intervention is required on the part of the player... just go about your business and enjoy the new scenarios as they appear.
The current version is v8

This mod expands on the depth of character and levels of interaction with the NPCs from the BG game. When BG2 was released, one of the major improvements in many peoples' eyes was the increased level of interaction one could have with the party members. This mod was developed to allow BG players a similar experience. NPCs in your party now have banters with the PC, with each other, and small side-quests of their own.
The current version is v16

Music appropriate to each NPC that plays whenever they initiate banter. This musical package is a separate, optional package to the BG1 NPC Project.
The current version is v5

Kismet (Amy Johnston) has ported the "Cloakwood Squares" parody/game show fanfic to the Infinity Engine. See Salvanas and Tiana fight a battle of wits with nine of your favorite BG2 NPCs, then watch as the winner matches up with Weathermistress Ada, all overseen by the Master of the Cloakwood Squares, Lord Keldorn Firecam!
The current version is v2

This mod expands Coran's Friendship talk sequence, adding up to eighteen (18) new banters with the protagonist, and one potential homosexual romance for a player character who is not in an active romance. If you have The BG1 NPC Project installed, they begin flirting after the last regular friendship talk.
The current version is v2

Started by Grim Squeaker, this mod will add new material for between various Baldur's Gate II mods including banters, romance conflicts and interjections. Contains an optional Crossmod Romance Conflicts component.
The current version is v7

de'Arnise Romance adds character development and a romance track to displaced debutante Nalia de'Arnise, late of the Keep and lately of the Copper Coronet. Male protagonists (Humans, elves, half-elves, and dwarves) now have an opportunity to woo Nalia while encountering threats new and old to the livelihood of the de'Arnise lands.
The current version is v2

This mod offers the player the chance to get to know everybody's favorite Red Wizard better. You will learn more about his thoughts, hopes and fears, as well as his past, and you will affect his future, one way or another.
The current version is v1.07

Flirt packs for the Edwin Romance mod.

The romance is available for females of all races, with Intelligence of 14 and above. It will carry on from SoA into ToB, and there is one new quest for Edwin in the SoA part, as well as new epilogues. For the male PC, there are some new interactions with Edwina. Be warned, some of Edwin/Edwina's desires may be NSFW!
The current version is v1.07

Based on the story of the same name, this mod adds a cutscene to the Kelsey romance. Irenicus is but a distant memory and Kelsey's life with his beloved is wonderful... except for the suitor who just won't go away...

This mod will enable you to send any BioWare member of your party home, just by asking the Fate Spirit to manage the flight plans. The Fate Spirit will also be happy to return former party members to the Pocket Plane for re-recruitment, at your request. The only thing this agreeable travel agent asks is that these NPCs actually be in the party when you make the request. The NPCs will leave their luggage behind, though, so there is no risk of losing either plot items or yummy loot.

IEP Extended Banters adds almost 60 new banters between Bioware NPCs in the Shadows of Amn portion of the game, extends most of the NPC conflicts to allow the PC to interfere, and includes a customizeable banter accelerator.
The current version is v2

This mod adds a full romance for Imoen. Currently SoA-only.
The current version is v1.201-PATCH

This is the add-on soundtrack for the Imoen Romance.

Gives the option of changing Imoen's kit, as well as introduces a few PnP changes to the overall game.
The current version is v1.4

You're offered a list of the NPCs who can join your party and share your kooky adventures. You can choose to tamper with some or all or none of them. Let's say you've chosen Minsc. You can assign him any class that a PC could have (Ranger Minsc! Fighter/Thief multi Minsc! Sorcerer... erm, Minsc!). After selecting a class, you can assign a kit (if you like). The list of kits you're offered is any kit that's installed in your game that the class you've chosen could select.
The current version is v1.1

This mod adds a quest to gain Mazzy a Paladinhood.