Any retail business worth its salt these days has to have an online presence. Whether it's a multibillion-dollar behemoth or an artisan craft shop on Main Street, a business that doesn't have an online presence is leaving gobs of money on the table. Shopify's (NYSE: SHOP) online retail platform makes it possible for any company of any size to have an online presence, and the stock's performance has been a reflection of the opportunity this business has.After a 557% run-up in Shopify's stock price since its IPO, investors might start looking for other upstart companies that could turn in a repeat performance -- or an even better one.