I've been hearing from various Red Cross
representatives on the radio and on television that they're
literally swamped with donors today (I'm sure they wish
they had THAT problem all the time). At any rate, they
emphasize that if you can't give today, please try to
within the next few days, as the need for blood will be
ongoing.
Also, if you can't give blood and are so inclined, you
can help by making a donation to the Red Cross,
either via phone at 800/HELP-NOW, or via secure server
at redcross.org.