Google has provided two sample Gadgets -- modular mini-applications. One provides a view of one's Google Calendar agenda, along with meeting alerts. The other shows recently opened Google Docs files and makes those files searchable from Gmail. The Gadgets can be enabled through the Gmail Labs tab in the Settings menu.
Google also has added a Gmail Labs option to "Add any gadget by URL," which allows users to add any Gadget, as one might using iGoogle. While not all Gadgets make sense with Gmail, improved synergy can be expected as Gadget creators start developing with Gmail in mind.
Gmail engineer Dan Pupius concedes this isn't the most user-friendly approach. "It's a sandbox mainly aimed at developers who want to play around with gadgets in Gmail," he explains in a blog post. "We're not tied to the [left-navigation bar] as a primary way to extend Gmail -- in fact we think it is relatively limited and doesn't offer scalable real estate. There are also some downsides to the iframe-style Gadgets we're using today -- they can sometimes slow down the page. We're fanatical about speed, so we'll be keeping a close eye on performance."
Google's Gmail service has been under more or less continuous renovation since Gmail Labs opened in June, with new features being rolled out every few days.
In October alone, Gmail gained emoticons for messages, Gmail for mobile version 2.0, canned responses, contact manager improvements, advanced IMAP controls, and Mail Goggles.
Gmail's relentless pace of change appears to be paying off with growth. It reached 26 million unique U.S. visitors in September 2008, up 39% from a year earlier, according to ComScore Media Metrix. Yahoo Mail remains more popular, with almost 88 million unique U.S. visitors in September, but it grew only 6% from the same month a year ago. Microsoft's Windows Live Hotmail had 44.5 million unique U.S. visitors in September, down 4% from twelve months earlier.