Picasa cannot be installed with package-manager because its license doesn't allow anyone to distribute it freely. But you can still install it by following these instructions:

The latest version

From http://pchilfe-juergens.de/PISI-Pakete/

From this site you can select and install Picasa.

From Google website

1. Go to http://picasa.google.com/linux/ and select (at this moment)

    Download Picasa 3 for Linux

   and select version

   deb, for Debian/Ubuntu

2. Open Konsole and check required packages

    sudo pisi it binutils 

3. Cd to downloaded .deb file

    cd ~/Desktop 

4. Use ar to extract the installation archive from deb

    ar x picasa_*.deb data.tar.gz 

5. Delete downloaded .deb file

    rm -f picasa_*.deb 

6. Move archive to top directory

    sudo mv data.tar.gz /. 

7. Goto this directory

    cd / 

8. Unpack archive

    sudo tar zxf data.tar.gz 

9. Delete the archive

    sudo rm -f data.tar.gz 

10. Add an item for Picasa 3 to K Menu

     kdesu kwrite /usr/share/applications/picasa3.desktop 

    After entering the root password an empty KWrite window will appear and Copy/Paste the following 7 lines in this window:

    [Desktop Entry]

    Name=Picasa 3

    Exec=/opt/google/picasa/3.0/bin/picasa

    Terminal=false

    Type=Application

    Icon=/opt/google/picasa/3.0/desktop/picasa32x32.xpm

    Categories=Application;Graphics

    Select [Save] and [Close] KWrite.
11. Close the Konsole
12. You can find Picasa 3 in Pardus > Programs > Graphics.