There's now one of those donation-matching pledges: http://new.thebiggive.org.uk/projects/view/13157
Can someone less lazy than me check to see how often they get the full amount? If they do, it doesn't do anything for the marginal donation, so it stops mattering.
As of today, GiveWell has two new top charities:
1. Against Malaria Foundation
2. Schistosomiastis Control Initiative
Their previous top charity, Village Reach, no longer has much room for more funding. Which is a good thing: partly through givewell's influence they now have as much money as they can put to good use.