You have a fantastic piece of software here, and I'm happy to have it
up and running on Linux now.  One thing that took me quite a bit of
searching was to figure out how to get Picasa to play nice with
Nautilus under gnome.  After some searching and a few issues, I found
the answer.

I needed to create the file:
/opt/picasa/bin/picasa-hook-filemanager.sh
Just putting it in /usr/local/bin, or anything else in PATH didn't
work, it needed to be in /opt/picasa/bin

Then I had to chmod it so it could execute, and finally here is the
contents:

nautilus "${1%%$(basename "$1")}"

This works perfectly, however I still had to go in and move/delete
winefile and winefile.exe.so because Picasa was opening the directory
in Nautilus, and then again Wine File.

So again, to recap:

$ nano /opt/picasa/bin/picasa-hook-filemanager.sh
add this to the end of the file:
nautilus "${1%%$(basename "$1")}"
save it
$chmod 777  /opt/picasa/bin/picasa-hook-filemanager.sh (or something
more secure else if you don't want it 777)
In Picasa, right click on a file and select Locate on Disk
Make sure it works!
If Picasa opens WineFile AND Nautilus, do the following:
$find -name winefile
rm or mv winefile and winefile.exe.so

To use Konqueror - I haven't tested this, but several people say that
entering one of following in picasa-hook-filemanager.sh will launch
Konqueror:

konqueror --profile filemanager "$1"
or
konqueror --select "$1"

Thanks for the great software - hope this helps someone!

Jon