It looks like I'm one of the fortunate few who managed to place an order. I had an account set up beforehand but didn't have my cart full until 10:45am or so. SparkFun was, indeed, exceedingly slow but my tactic of pressing "refresh" every minute or so seems to have paid off. I'd say it was an hour's worth of effort in total. Best of luck and keep trying!
What was the page you saw after clicking sth like "Yes, i want to get this stuff by Sprakfun Free Day"? I was able to get only to that moment and the next site (after a milion of "refresh") is just blank... Do you know anything about it?
The page went blank for me too after pressing "yes, I want free stuff..." but refreshing that blank page 10-20 times got me to a "congratulations" page with a SparkFun guy wearing a crown and an order email in my inbox (though my order total, which was well over $100, didn't reflect the $100 off I'm assuming it came through...but I saved the congrats page just to be sure).
Honestly, for me it was just refreshing every time the connection crapped out. Nothing else seemed to work. I bet they're getting hammered now though so it may take longer than the hour I got away with at 11am.
Oh man, that's rough. According to Pahalial, above, they had to restart apache so it may be worth trying again in a while when they have things sorted out more and when the blank screen frustration's worn off...a bit.