Google Wave closure
Google announce the closure of Google Wave:
As of January 31, 2012, all waves will be read-only, and the Wave service will be turned off on April 30, 2012. You will be able to continue exporting individual waves using the existing PDF export feature until the Google Wave service is turned off. We encourage you to export any important data before April 30, 2012.
If you would like to continue using Wave, there are a number of open source projects, including Apache Wave. There is also an open source project called Walkaround that includes an experimental feature that lets you import all your Waves from Google. This feature will also work until the Wave service is turned off on April 30, 2012.