I'm a fan of GetGlue. In just a matter of days it became the software I'd use to work out what book to read next. Software because I use it mainly as an Android App but it's a pretty slick web site too.
CEO Alex Iskold posted some impressive checkin stats today. They hit over 10 million check-ins and ratings in September. Just look at that ramp up.
GetGlue has the attention of some impressive names too. Play.com, for example, (disclaimer; client) is integrated with GetGlue so you can socially browse, like or discuss DVDs as you consider your next purchase.
The screen grab below shows what the Caprica: The Feature Length Pilot looks like, at the bottom of the page, with GetGlue installed.
You don't actually need to install anything to use GetGlue. I find it incredibly helpful for social media research though.