Not only has Westley (the creator of WeiDu) given us a way to EASILY add mods into our game, but he is an excellent modder as well. Below are his mods mirrored here and packaged in an easier to use zip format for Mac users:
Mod Name: Solaufein NPC Mod v100
I have yet to play BG2 long enough to get to the Solaufein of Ust Natha NPC. But from what I hear it is a mod that is greatly enjoyable. He has plenty of dialogue, his own challenges (one specifically for ToB), can romance the PC regardless of race, gender, or other stuff, and much more.
Mod Name: Improved Tactics v2.1
I love the tactics mod! The Tactics Mod Pack adds quite a few optional components to BGII. They all aim to make the game more challenging and rewarding by increasing the difficult (and thus the thought required) of encounters. Many of these components have been drawn from different mod authors; He did not write everything here. In particular, Gebhard Blucher, Kensai Ryu, Xyx and Ishan have made contributions. There are many (optional) components that you can add to enhance your game:
The Ritual (requires ToB)
Improved Irenicus
"Red Badge" Poison-Based Encounter (requires ToB)
Improved Undead
Anti-Paladin Kit
Mike Barnes' Improved North Forest (requires ToB)
Tougher Druid Grove
And TONS more
Mod Name: Ascension v1.4.17
The Ascension mod changes the end of the Throne of Bhaal expansion to feature extended roleplaying and tactical opportunities. It was written by David Gaider and members of the IEEAIS group.
Mod Name: Ease of Use v2.8
This mod is jam packed with a LOT of useful things that will make playing the game more fun than without it. Some of the features include:
Infinite Weapon and Potion Stacking (SoA/ToB)
Shut Up "You Must Gather Your Party ..." (Baldurdash)
Wear Magical Armor and Magic Rings
XP Cap Remover (Baldurdash)
Bottomless Bag of Holding (Blucher)
Romance: Any NPC Regardless of Race/Gender
Romance: Multiple NPCs Concurrently
Low Reputation Store Discount (Sabre)
And much more
Mod Name: Item Upgrade v3.2
The Item Upgrade mod allows Cromwell and Cespenar to upgrade additional items in BGII. One third of them are convenience functions (e.g., they save you ring or boot space), one third of them try to beef up categories of weapons that are "weak by comparison" (e.g., clubs and spears), and one third of them upgrade NPC-specific items.
Mod Name: Spell-50 Mod v6
The Spell-50 mod extends a number of priest, druid and mage spell effects to level fifty. Spells cast by friends and enemies alike are modified. Basically, it's a mod for players who would like to see phenominal cosmic spellcasting at higher levels. I wouln't advise using this unless you either want to lose the fun factor OR want to get your butt kicked... a lot.
Mod Name: Unrepresented Items v2.0
The Underrepresented Items mod blatantly steals some items from Icewind Dale 2 in order to flesh out some item groups in BG2 that are, shall we say, a little light for early game tactics (e.g., darts, maces, halberds). Note that unlike the Item Upgrade Mod, we don't claim to be particularly balanced here (although these items were "balanced" in IWD2, they may well be egregious in BG2, the jury is still out).
Mod Name: Valen NPC v4.1
Valen (of Bodhi's hold) becomes an NPC who can join your party. She's a Chaotic Evil Vampire fighter/thief. This mod was fun, but I found that just by taking her on you lose a lot of rep. And she likes to get nasty... no let me rephrase that. She likes to get NASTY. Although fun, I wouldn't advise using this mod unless your PC is of an evil alignment.