You can use the Picasa Web Albums uploader tool to download albums that you own. I think this tool works with non-Intel machines.
If you have an Intel machine you can use Picasa for OS X to download albums you own - and, more importantly, shared albums from other people.
I've done the latter. It works - but it's a pain. Read the documentation: Downloading Albums and Photos. Here are a few additional notes to help out:
- When you install Picasa it starts indexing your drive. Go to Tools:Folder Manager and mark every folder as exempt. It will stop indexing.
- Don't bother looking for the option to download from an album URL. It's not there. Yes, this is very weird.
- Go to the shared album and look for the 'Download' menu item. Click on it. You may see that 'Download to Picasa' is unavailable -- grayed out. That's because you need to quit Safari and restart after Picasa is installed (and perhaps running). Now you should be able to see this option. Click it.
Picasa stored my images in Pictures\Downloaded Albums. I dumped them from their into iPhoto then deleted them.