Picasa is one of the most popular online photo publishing services available. However, it has always been a place to publish your photos for others to see. Now Google (the owners of Picasa) have introduced Collaborative Picasa Web Albums. Every album on Picasa Web Albums is potentially collaborative: multiple people can add pictures to the same album.
You can now create a Picasa account and then your, your siblings, your cousins, and others can upload pictures to the same albums. This should be a great method of sharing family photos, whether they be from the late 1800s or from last week's family reunion.
To make an album collaborative, sign in to Picasa Web Albums and add contributors. Just click the 'Share' button, add contributors, and leave the 'Let people I share with contribute photos' checkbox selected.
You can also manage access for contributors you've added to the 'Shared with' list by toggling the 'plus' icon next to their name – when the plus icon is green they can add photos.
Contributors will need to log in to Picasa Web Albums with their Google Account to add photos. When they visit your collaborative album, they just need to click the 'Add Photos' button to start uploading.
Contributors' photos will be attributed to them, and they can rotate, delete, or add captions to the pictures they've uploaded.
You can learn more at http://picasa.google.com.