I've had a play with Tumblr before and started a new one today. If you are not familiar with it Tumblr is (yet another) blogging platform though stands out from the crowd a bit by falling between traditional blogs and microblogging like Twitter. Its usually used for quick sharing of links, videos, ideas and the like and has inter connectivity built into its DNA.
The inter connectivity of Tumblr is key to why i want to use it. If i post to it then that post is automatically sent to my Facebook and Twitter feeds too so i only have to post cool stuff once. Lazy social media!