InstaGrok is a promising new academic search engine and bookmarking service that I've written about twice this spring (here and here). Unfortunately, according to their Twitter posts, they have had a server crash. If you're trying to use the service today, bear in mind that it might not be working completely or at all right now. Even though they Tweeted that it's back online, not everything appears to be functioning correctly. I'm sure they are doing their best to get everything restored quickly.
instaGrok is back up from a crash of our server
— instaGrok (@InstaGrok) May 24, 2012