Twitter, Groupon, Zynga, Facebook: It seems each day brings a new valuation in the tens of billions of dollars for the next big Internet startup. 10 years after dot-com robber barons like Mark Cuban made a killing off of code, the richest, most powerful people in the world are once again rocking t-shirts, flip-flops, and bed-hair.

With venture capitalists habitually flocking to a rash of new hotbeds of online innovation (SXSWi, Y-Combinator, Disrupt, etc.) with bags of cash at the ready, have we found ourselves in a new Internet bubble? Time will tell. Just yesterday Instagram, one of the most popular new social networks, was acquired by Facebook for $1 billion. The purchase raised the eyebrows of tech insiders and casual users alike. But really, that was nothing. Hot Internet properties have sold for way more. Follow us in a countdown of the Internet's biggest paydays to see how we got here—and what today's Big Thing might look like tomorrow.