I recently got sent a link to a Picasa album online and wanted to download the whole album without having to install Picasa.
The solution was to install the DownThemAll add-on in Firefox and use that to download all of the images in one go.
These instructions are for Firefox 4.
Click the Firefox button at the top left hand side of the Firefox window and then click Add-ons:
In the search bar at the top right hand side of the screen type down them all and then press Enter.
Scroll down and click the install button that belongs to the DownThemAll add-on:
Next goto the Picasa web album that you want to download (for me this involved simply clicking on a link that I was sent in an email).
On the right hand pane click on the RSS link:
Right click and select DownThenAll from the menu:
In the DownThemAll window you change change the destination directory if you want to – otherwise just click the Start button to begin the download:
This worked for me and was preferable to installing some software that I would otherwise rarely use.