It's Talk Like a Pirate Day, and to celebrate, LibraryThing is holding a scavenger hunt. If you solve five of the riddles and find their corresponding LibraryThing pages, you'll be upgraded to a free lifetime membership.
LibraryThing has a bit of a learning curve, but I like using it to back up my reviews (unlike Booklikes, you can export your catalog) and keep track of my book collection (both what I have and where it's located). At any rate, if you want to give it a go, this is a nice way to get a lifetime membership so there aren't any limitations on how many books you can add to your catalog. Basic free memberships are limited to only 200 books, or whatever else you choose to catalog.