Google Gears is an open-source browser extension that enables access to online services while offline. For example, using Gears you can continue to read un-read posts in Google Reader even though your no longer connected to the internet. Then, when you are connected again, the offline cache syncs & refreshes. I know this is going to make a BIG difference in my ability to wade through un-read blog posts!
Given the open-source nature of the software, developers will be able to make any website 'Gears enabled' so that browsers can continue to read it offline.
The important point for Google is that by combining Gears with the impressive Google Docs they will start to get some further traction in the fight for our desktop space, against rivals Microsoft and their Silverlight product.
Read more on the new Gears blog.