Can you duel wield weapons in BG2? Also, what are the familiars (if any), and which classes have which familiars?

Yes, you can dualwield weapons in BG2.
Sorcerers and mages get familiars, but only if they are the main character (i.e. NPC mages can't get a familiar).
Good characters get a Faerie Dragon or Pseudo Dragon, Neutrals a Cat or Ferret or ? (forgot the third option) and Evil characters an Imp or Quasit (depending on their inclination towards Law and Chaos).

Third option is (DON'T LAUGH) A rabbit. (I CAN HEAR YOU LAUGHING!) but it all depends on your alignment. It'll give you a discription of what familiars you can get in the spell description.
And yes you can dual weild weapons. Simply put a weapon where the shield should go. i warn you though, you should have three "stars" on the dual wielding option or you will suffer MASSIVE THAC0 and damage penalties. The best class for dual wielding is a ranger...they already come with 2 stars on dual weilding.

Thanks Kaltia... LOL, I'd written down rabbit in my original reply, looked at it and thought "no, surely that can't be right" :D

you can only dual-wield one-handed weapons with no ranged capability (no throw axes) and with no two-handed or ranged weapons equipped in other slots.

Actually, it's not just Mages and Sorcerers--it's ANY character who can cast Wizard spells, which includes Bards (and Multi- Dual-classed Mages) as well.

I thought only a special kind kind of mages can use familiars.

At least the ones able to cast the Find Familiar spell, of course. For instance if the spell is part of an opposite school of Magic. ;)

The rabbit is cool.

Neutral evil mages get a mephit as a familiar. The ranger kit beastmaster also gets a familiar.

I generally think that the neutral familiars are the coolest. Their thieving skills can be useful in non-combat situations.

The magical skills of the good and evil familiars are really only usable in a combat situation and I guess that you are wise enough to keep your familiar away from any real combat.

I usually use my familiar to yell obscenities at passersby and use all the dialogue options my main character won't use.

The ferret is by far the cutest familiar.

thieves with the high level ability "use any item" can also get a familiar if they cast from a scroll, although this generally applies to ToB.