Another of those things that are already well established but I discovered them just recently:
Flickr.com is a service to store and display your digital photographs. You can use it for free if you don't upload more than 20MB of pictures in a month (the storage itself is unlimited, there's just the limit for uploads). They recently abandoned their quirky Flash interface and almost everything can now be managed cleanly using a few DHTML tricks. It's certainly much easier than you'd imagine when you read the words "web-based photo management". It also works exceptionally well with blogger.com, allowing me to publish a post with photo taken with my mobile phone camera right from the camera (provided the camera can send standard e-mails with JPG attachments, which most of today's middle-range phones can).
Using Flickr, I can automatically show you the latest photos I uploaded (see the "Flickr badge" at the right side of this page), our dogs, our cat, everyone's cats or Mr. Jesus C., the athlete (hung up in Prague's Lucerna Passage). I don't know what art is but I know what I like!