Google has put in a tremendous effort in fine tuning almost all of its fleet of web services to work on iPhone over mobile Safari. First, it was their search page, then came gmail, and finally, it even rolled out to Picasa Web.
This free online photo service is practically identical in terms of functionality on the iPhone as its desktop browser version. You can quickly access your albums, view photos w/ captions, add /read comments or even start a slideshow. The connection of WiFi is preferred but respectable over EDGE.
However, editing, organization, album properties and email link features are non-existent. Considering the nature of photography and sharing and the lack of copy & pasting in iPhone, an integration with Gmail to send the album link would be much appreciated.
I've taken a few shots for your reference, click on them to enlarge. Enjoy!