Lately I've been trying to extinct my Yahoo! usage and get rid of that account altogether, but that would mean deleting my (paid) Flickr account as well. I have thousands of photos stored there, though people rarely stop in and look around. I'm exploring free alternatives: Photobucket is an excellent containment facility for lots of photos but I think they have to develop their layout and navigability to something less clunky, more intuitive. Adobe Photoshop allows you to upload, modify, and store photos online. For that matter, Facebook and MySpace both have reasonable photo gallery functions.
But in terms of multi-platform compatibility, I'm going to spend more energy exploring how Google (Sites, Maps, Profile, &c.), Picasa, and Blogger work with each other. I've only started to explore their features and capabilities, I know they're capable of much more than I'm aware. I don't expect anyone else to follow me down this path, but I will make it easy for anyone to see what I'm doing.
For instance, here is a link to my collection of Holga photography. This is just about everything I've done with the Holga (and there might be some Diana shots in there as well). I even have it set up so that when I store anything in my Holga folder on my computer, it will automatically upload to my online Holga folder as well. I'm very excited about the potential for this, for getting all my operations running in one sleek little ring rather than asking a bunch of unrelated programs and sites to pull together for me.