Cost: Free to use, but Carvana takes a percentage of each sale. Though buying cars strictly via the Web without a traditional bricks-and-mortar dealer has been long talked about, Carvana is betting the concept is ripe for an upgrade. The online preowned-vehicle service uses a mix of immersive photography, custom search features and home delivery to offer a surprisingly deep inventory of pre-owned vehicles without the hassle and expense of dealing with a traditional used car dealer. "What we try to do is do away with what we estimate is the $2,000 per vehicle cost of selling a car in a bricks-and-mortar retailer." says Carvana's Garcia, "Our per-vehicle cost is closer to $500, and we pass that saving to customers." Carvana is far from the only direct over-the-Web auto play. General Motors ( GM) has been flirting with its Shop-Click-Drive Web initiative, and there are plenty of used car deals from Craigslist to Carmax ( KMX). But Carvana's compelling shopping experience makes me think the bar is about to be raised for selling vehicles online. Auto selling on the Web might just be a hot topic this year.