Picasa Web Albums, the online extension of Picasa, has recently added tags and search. Now you can see a tag cloud in the right sidebar of a public gallery (instead of increasing the font size for frequent tags like in Flickr, Google chose to show the number of photos that have a certain tag). This way, it's easier to explore someone's photos without going to each album. The number of photos you can upload to an album has been increased from 300 to 500.
Source:→ Google system