Google waited until late today to announce Google Gears, which allows you to run Gears-enabled apps in 'offline' mode. You can use this in Google Reader, for example, to download the latest 2000 messages and then browse your feeds far away from any WiFi connection. Actually, that's all you can do right now as that's their demo, for now, but you can easily imagine all of the major Google Apps -- Gmail, Calendar, Docs, etc... -- getting a similar treatment. They've already released an update to the Google Web Toolkit to support Gears.
As is, it's definitely a 'beta' for me: I had to run the installer twice and the Google Reader extension doesn't download any images. Images are the primary way in which I filter entries to read, so I can't see myself really using this extension just yet. Update: I may have to already uninstall. Google Reader has asked me five times this morning if I wanted to switch to offline reading mode ("Connection error: A connection to the internet could not be made. Would you prefer to read in offline mode?"). I'm reading from a wired connection at work, this is downright annoying.
Also, Google will hardly be the only provider of this sort of technology. Firefox 3.0 will ship with similar APIs out of the box and Adobe's Apollo toolkit does the same. Hopefully we won't end up with 20 different offline synchronization programs that we have to download and install just to use the Web. Google took a positive step by releasing this as open source and indicating that they are willing to work with Mozilla, Adobe, and Opera.