Picnik's rich editing tools are now integrated into Picasa Web Albums allowing you to experience them without ever having to leave your account. As long as you're using Picasa in one of the Picnik supported languages, just click 'edit' from the edit drop down menu or from the new handy Picnik icon.
Then, Picnik away by applying an effect, adding a sticker, or exploring your own creative path with advanced tools. When you are done editing your photo, save back to your album by either replacing the existing image or making a new copy.
Sometimes 1+1 really does equal more than 2.
Happy Picniking (from right inside of Picasa Web Albums)