If we weren't Mac owners happily using iPhoto, the second best option would probably be Picasa from Google. It's a nice way for Windows users to organize their photos.
However, a nice feature that Picasa holds over iPhoto is the ability to make free Picasa Web Albums. All you need is a Gmail account and off you go, uploading directly from Picasa. (If you aren't yet in on the on the limited testing of Picasa Web Albums, you'll want to hurry and visit the Picasa Web Albums site and sign up. No telling how long they'll be handing out invitations.)
Well finally Mac users get to get in on the game. Google has released the Picasa Web Albums Exporter for iPhoto. Now, you can upload directly from iPhoto and share your pictures online in no time.