Currently Mac users' best option is to install an iPhoto plugin to export to a zip file, then use a web page to upload that file. Create a seamless uploader or integrate with an uploader someone has already written.
Better options now:
The Picasa desktop client (intel macs only)
Pixelpipe
The Picasa desktop client (intel macs only)
Pixelpipe
brlewis posted on 2009-04-09 21:26:44