First, you have to fetch the picasaweb album RSS link (located in the right column). For example:
http://picasaweb.google.com/data/feed/base/user/mesher7909/albumid/5482956614732347265?alt=rss&kind=photo&hl=fr
Then this little command line will download in your current directory all the full size photos of this album:
URL="http://picasaweb.google.com/data/feed/base/user/mesher7909/albumid/5482956614732347265?alt=rss&kind=photo&hl=fr" curl -s "$URL" \ | xmlstarlet fo \ | grep "<enclosure" \ | sed 's/.*url="\(.*JPG\)".*/\1/gi' \ | sed 's/\(\/[a-z_\.0-9-]*\)$/\/d\1/gi' \ | wget -nc -i -
Needed packages:
sudo apt-get install curl xmlstarlet