I have been a big fan of Picasa for some time and regularly use the Web Albums application to upload photos for sharing. Picasa is one of the easiest photo management tools to master and, I think, easily outperforms iPhoto. Picasa 3 (beta) has a slew of new functions that enables users to do all kinds of things. I’ll let the Google guy lay it out for you:
Not sure when we will see Picasa for Macs but I certainly hope it is sooner than later.