My favorite tumblr of the week is "If You Can't Say Anything Nice."
Not only is the author's avatar a picture of 1960's style Batgirl, but it's pretty much full of amazing. Videos of people singing in zoos, highlight clips from The Mighty Boosh, the occasional fantastic original video, and pictures of stuff I like to look at. What more could you wish for?
An example of the gems you'll find there: