Chemistry.com is having a free weekend starting Friday, July 20th and running until Sunday, July 22nd 2012. Unless I’ve missed some, this is the first free Chemistry.com weekend since May.
Sign up to try the Chemistry.com Free Weekend
Clik here to view.

Unlike some of the other free events, the Chemistry.com free events generally include all the features of the service during the free event so if you’ve been on the fence about trying, this weekend should give you an idea of how well the service could work for you.
Good luck to anyone giving the free weekend a try!