Even though the global initial public offering (IPO) market is slowing, some of the companies with the biggest IPOs of all time are still going strong. That's in addition to recent IPOs that have generated massive returns for investors. Don’t Miss: Until 2016, it was illegal for retail investors to invest in high-growth startups. Thanks to changes in federal law, this Kevin O’Leary-Backed Startup Lets You Become A Venture Capitalist With $100 Airbnb was worth $47 billion at IPO. This New ‘Airbnb