Picasa is a program developed by Google, Inc. whose function is to allow the user view and organize the pictures in his/her Mac.
Picasa searches for all the images in your HD and shows them on an eye-catching and intuitive interface. Without any doubt, the presentation is one of the high points of this applications.
It includes some advanced features really easy to use. Picasa allows you to burn your pictures in a CD and it creates slideshows on fullscreen.
You can configure the printing options as you desire and allows you to extract the photos from your digital camera. Now, and thanks to Picasa you will have the album you desired and you will be able to see your photos anytime you want.
Notes

For Mac OS X 10.4.9 or higher.

Picasa Google For MacNews

It includes the new face recognition system and batch tagging.

Google Picasa Download For Mac

Photos Resources‎ > ‎Photos & Picasa FAQ‎ > ‎Picasa‎ > ‎General information‎ > ‎

How to get the final Picasa version

Google stopped supporting Picasa3 on March 15, 2016, and removed the installation file from the Picasa and Picasa Web Albums Help website. Read more about Picasa's 'retirement'.
The latest version for Windows computers is Picasa 3.9.141 Build 259
The latest version for Mac computers is Version 3.9
See below for directions how to find the latest Picasa installation file for Windows and Mac.
If you have already downloaded the Picasa installation file, save the file to several different places such as external drives, flash drives (USB), CDs, Google Drive. You would use that file whenever you need to install or reinstall Picasa3 to another computer, to install after your computer was reformatted, or for any other reason you need to reinstall.

For Windows users

A contributor (Product Expert) has made the final Picasa3 setup file for Windows available at OneDrive:

For Mac users

At your own risk: https://picasa.en.uptodown.com/mac
We have been informed that this does no longer work on the latest Macs.
Any feedback on this thread at the Photos forum would be welcome.
Mark your post as an answer, that triggers an email to those who subscribed.
How to install the latest version
  • Check your version of Picasa by going to Help > About Picasa
  • In the 'About Picasa' box under the Picasa logo is the version and build number
  • If your version is earlier than the final version 3.9.141 build 259, do the following:
    • Locate the latest version of Picasa .exe file (see section above) and run the installer over your previous version
      • You don't need to first uninstall your present Picasa version
      • The installation process will find the existing Picasa database and photos on your computer.
      • Your photos exist on your computer and will not be harmed or lost during an installation
  • If Picasa fails to install, then uninstall your present version, go to Tools > Options > General tab. Under Automatic Updates, change to 'Don't check for updates' then click OK. Install the latest version of Picasa.
  • For Ultra HD-screens (Windows): right click on the Picasa-icon on desktop and choose Properties > Compatibility: you can switch-on an option for High DPI.
Please see 'Quick Start Guide' for more help in setting up Picasa

Release Notes

https://sites.google.com/site/picasaresources/Home/Picasa-FAQ/picasa/general-information/release-notes

Download Picasa For Mac Os

Picasa is an easy way to find, edit, and share your photos. Manage your photos in one place, and find photos you forgot you had. Eliminate scratches and blemishes, fix red-eye, crop and more. Picasa is a software developed by Google, Inc. Whose function is to allow the user view and organize the pictures in his/her PC. Picasa searches for all the images in your HD and show them in the eye-catching and intuitive interface. Without any doubt, the presentation is one of the high points of this applications. Google Photos is the home for all your photos and videos, automatically organized and easy to share. Picasa is a cross-platform image organizer and image viewer for organizing and editing digital photos, integrated with a now defunct photo-sharing website, originally created by a company named Lifescape In 2016, all the photos were migrated from Picasa Web Albums to Google Photos and development on the Picasa desktop was stopped.