Not a whole lot. You can bind your allies' lifeforce into a web, such that casting a spell on one affects everyone interwoven. Takes 10 minutes to form, lasts 24 hours, max number of allies equal to your int or cha bonus, max level of spell you can distribute is equal to your war weaver level. It's basically mini Chain Spell, but only for allies.
Range doesn't change (until 5th, where it increases by one step) so even if you cast a Bull's Strength over the web, you still need to touch everyone. If the spell has a costly material component or an exp component, you still have to pay it for every recipient. You cannot extend personal range spells over tht web.
The other thing they can do is store spells in the web to be triggered later. 1 spell at 2nd, up to 4 spells at 5th. Max level per spell equal to your war weaver level. You can trigger the spells as a move equivalent action, and the range restrictions still apply when you trigger the spells. For example: if you've stored a Bull's Strength and a Haste, when you trigger them, everyone has to be within 30' of one another to qualify for Haste ... and you have to be able to touch all of them (as part of the same move equiv action) to qualify for Bull's Strength.
As already mentioned, at 5th the spells you cast over the web increase by one range category, so at that point your Bull's Strength can affect allies within Close range instead of having to touch 'em all, etc.
That's War Weaver in a nutshell. Now you know, and knowing's half the battle.