America Online has developed a web-based email service called Alto (altomail.com), and early reports sure sound promising. Alto is not a new email provider (no @alto.com email addresses, at least not yet), but an inbox-replacement for your current email address(es). Read your Gmail, Yahoo, Mac, or other accounts; import Facebook, LinkedIn and Twitter messages. Nicholas Carlson at Business Insider has a review. Mat Honan at Wired gave it a whirl. Daniel Terdiman at CNET liked it. The service is launching as a private beta, with public availability sometime in Q1 2013. Alto is free for now, but expect ads or a paid "premium" option later on. It's browser-based, and there's an HTML5 version optimized for iPad (and, presumably, other tablets).
(Screengrab from Business Insider's review.)