Domain parking firms like Sedo. Also profitable as ROI might mean a small unheard of startup could be more profitable than Google in terms of relative profitably but just on a smaller scale. For example, ecommerce B2C firms, selling moderately priced items, whose operation is only made possible with the web could theoretically be more profitable than the ones you mentioned.<p>Eg: "SnapNames and its competitors would then auction off deleting domains, generating an average of $100 per domain (with some going for $100k or more). SnapNames was recently acquired by Oversee.net for $35 million, based on yearly revenues of around $40 million and profits of $3 million or so."<p><a href="http://www.techcrunch.com/2007/10/05/domain-industry-intrigue-overseenet-gets-hosed/" rel="nofollow">http://www.techcrunch.com/2007/10/05/domain-industry-intrigu...</a>
There are a huge amount of online businesses that are very profitable. This shouldn't take much research to figure out.<p>At Hotjobs we were doing significant revenues ($>100M) in 2000, and that was almost a decade ago.<p>On a more interesting note, start looking at net income for these companies.