Source: http://lifehacker.com/5729801/rrrewind-is-a-wayback-machine-for-social-media
Rrrewind is your ticket to social media's past, letting you browse the archives of the most popular items posted to sites like delicious, Reddit, YouTube, Hulu, and more.
Using Rrrewind is pretty simple. Upon visiting the site you'll be presented with the popular posts from yesterday, currently defaulting to delicious. You can switch between different sites via the lefthand menu, or visit the archives by clicking the link in the upper righthand corner. Currently Rrrewind's archives date back to June 29th, 2009 for delicious, but it varies depending on the site. If you're looking for old, popular social media, Rrrewind is a great place to find it.
Rrrewind | Thanks for the tip, Roberto!