I posted this over at the official forums but when I think if mods I think of Sorcerer's Place. I know that a definite load order isn't available for BG2. I'm hoping for some guidance anyway. Here's my mods:

1PP Flaming Swords
Bag Bonus
Banter Pack
BG2SoA
Blood of the Martyr
Cespy Audio
Fairy Dragon
IEP Banters
Imoen Impish
NPCFlirt
NPNPC Portraits
Planar Teleport
Stuff of the Magi (now in Weidu!)
Teleport
Turnabout
Unfinished Business
Wild Mage
1 Pixel Productions
Ascension (probably installing during ToB so I can see both endings)
BG2 Fixpack
BG2 Tweaks
D0 Quest Pack
D0Tweak
G3 Anniversary
Improved Horns
Improved BAMs
Oversight
PnP Celestials
RE v3
SCS II
Sequencer Memory
Longer Road OR Redemption (opinions sought)

Some of them that seem minor (like Sequencer Memory) I'm not too worried about. If I'm not mistaken if it's Weidu I'm golden too. But then I've heard things such as installing BG2 Tweaks and Fixpack early or late, I forget which. Any help in organizing this large number of mods would be appreciated.

I'm just going to quote what I posted a couple of days ago:

First off, read each mod's readme for installation instructions. In the absence of instructions on ordering, here's the general order:

Install these first (in order):
SOA
TOB
Official Patch
Non-weidu mods
Baldurdash or G3's BG2 Fixpack (I prefer the latter).

SCS II should be installed last (if you plan on installing it).
BG2 Tweak Pack should be second last.
Level One NPC's should be installed after any mod which adds kits, so that the Level One mod will recognize them.

All other mods should be installed somewhere in between.

Thanks. I remember asking about Tutu. I didn't remember asking about BG2. This gives me something to use as a guide. It was a little intimidating looking at all the mods and some of them are .exe so the readme is buried until install. I'll use this guide.

Ascension needs to go first.

(In fact, consensus seems to be that it should even go before Fixpack.)

I've already started installing non-critical mods like IEP Banter. Should I do a fresh install and then do Ascension first after the patch?

yes :)

Installing Ascension after fixpack will, at the very least, wipe out a big bunch of bugfixes to (mostly) protective spells.

I've gotten a few different suggestions through different boards. I followed this advice as well. Just need to install BG2 Tweak and I'm game on!