John Murphy (whose small performance troupe the Anunnaki Group is included in GiveBig) makes this point on Facebook:

It is IMPORTANT to recognize that the people who are at a major disadvantage in this program are the smaller arts organizations who have less of an ability to get a piece of the pie in what is essentially a competition between david and goliath. Choose wisely, choose to help out the 501(c)3's that do not have the finances to afford a marketing division. Many small arts orgs in Seattle are falling behind for their relative piece of the matching.

GiveBig's whole list of orgs to donate to is here, with arts and culture specifically here. All the big players are there, and rumor has it that many asked their donors to wait until today to give, in order to maximize—which makes sense. But given that the spirit of this thing is leveraging the big (rich) to help the small (nonprofits), you might be inclined to consider leveling the playing field before the money pot is full at 7 tonight. Here are a few small, deserving shops I can recommend in art: Photographic Center Northwest, Pottery Northwest, Kirkland Arts Center, Jack Straw Foundation, Arts Corps, Path With Art, The Alliance for Pioneer Square, Northwest African American Museum.

And don't forget the happy hour starting at 4 at Vermillion to celebrate GiveBig in the arts!