Tumblr is one of the newest, fastest growing social media sites out there. If you're unfamiliar, it mixes the succinctness and ease of Twitter, the niche community aspect of old Livejounal (if you remember those), the personalization and customization of Myspace, and the commenting/like functions of Facebook.
The result is a vast selection of micro websites, many of which are more like endless image galleries. This medium is perfect for fashion and brings a whole new life to vintage too. Though lots of personal sites blog vintage things on Tumblr, there are pages 100% devoted to vintage. If you have a Tumblr account, you can easily like a post and have that post saved automatically so that all of the images you love are all together in one place, and you don't have to save it to your hard drive (my favorite part).
Here are some of the best vintage related Tumblrs worth following or looking through:
Draw This Dress (Fashion From Old People)
Bad name, but an interesting Tumblr. A different take on just reblogging everything in sight. Ther writer intrupets photos of vintage outfits into illustrations. You have to see it for yourself!
Valentino Vamp
Goregeous black and white portraits and head shots of famous/infamous/important women of the twentieth century. I especially love the ones of silent film stars.
The Swinging Sixties
Not much explaination needed; all 1960s images. From ads, to film stills, to editorials, it's all a vintage lover could ask for.
Vintage Quality (SO Vintage)
A hodge poge vintage ephemera, inspiration, and beauty from the 1930s - 1960s. Lots of great fashion photography and fun images.
Women of the Sixties (Welcome to the Sixties)
Pretty self explainetory: great pics of all kinds of women in the 60s: famous ones, regular ones, models...they're all here.
A Conversation on Cool
Awesome candid shots of "cool" people in the 20th centrury doing "cool" things.