In February, Google announced that the Picasa desktop application would no longer be supported from 15 March 2016. This page is an unofficial mirror that will allow you to download Picasa after this date.
For those of us looking for a simple yet flexible photo editor that works locally on your computer, Picasa was the answer. The replacement, Google Photos, is pretty cool, but it's only good when there is an internet connection. As a way to organise photos on your computer, I have yet to find anything better.
You can download Picasa using the link above. Note that I am offering this download as a mirror only. This software was created by Google and is now unsupported, including for bug fixes and security updates. Use at your own risk.