With Picasa Web Albums, you get 250MB of free storage--enough to post and share approximately 1,000 photos for free. But it's so easy to put your photos online that you just might want more storage. For $25 a year, you can upgrade to an additional 6GB of space (25,000 photos' worth). Whatever your needs, Picasa Web Albums is perfect for amateur and pro photographers alike.
Picasa Web Albumbs allow you to publish privately or publicly. They also provide RSS feeds of your images. And as far as innovative features go, this page states
If a friend shares an album with you, you can do more than just view it on the web. With just one click, you can download the album right back into your Picasa to keep a copy for yourself.
You can leave comments on friends' photos, as well as give captions to your own. And if you've already given your photos captions in Picasa, the same captions will be there after you upload them to the web.