Two days ago the First Public Working Draft of Web Notifications was published. The idea behind this specification is to let web applications integrate with the notification system of the operating system. Or with a third-party system (e.g. Growl on Mac OS X). As there has been some confusion in the past I should stress that this is solely an API for showing a message to the user that e.g. a new email or instant message has arrived. This is not push technology; it is not for streaming data over the network.
The main outstanding issue at this point is how the user can opt in to a web application using this functionality. We do not want to allow it by default as that would create a lot of spam (see popups). However, asking permission from the user might not be the best solution either, as users often do not really know what they are agreeing to. And it will get unwieldy if more such APIs are added. We already have storage space (when localStorage is about to run out a user agent can ask the user for more space), location (getCurrentPosition()), and asking whether a given site can be the default handler for a particular type of URLs (registerProtocolHandler()). Google’s attempt at tackling this problem is installable web applications, though whether that is a good idea remains to be seen.
Anyway, if you have ideas about either Web Notifications or the user interface problem, please contribute them. Who knows, maybe it is a good idea and everything can move ahead a little faster!