screenshot of .svg animation at 499 x 438 pixels
Following up on a post here titled "After Animated GIFs, What?" (and see also). I got an email from pac-n-zoom which has been working on web-based animation using .svg files (vector-based, essentially an open-source version of Flash). I made a test animation and if (but only if) you are using Firefox you can see the results here.
Down-sides to this so far in comparison to GIFs: (i) not enough browsers support it, (ii) the larger the file size the bigger the CPU hit, (iii) lack of tools to make .svg files.
Up-side: (i) open source, no-plugin-required animation (although pac-n-zoom will charge to convert raster to vector once they're out of beta), (ii) animation stays crisp and detailed as scale is changed, unlike GIFs, which fuzz out on most modern browsers. (because of)
(Also, for what it's worth, the WordPress software wouldn't let me load an .svg as an image, due to "security concerns." Had to use FTP.)
Update/clarification: I posted the .svg on a separate page because I knew some browsers wouldn't read it and didn't want an ugly [X] or what have you in place of an image on the main blog page. Not being able to upload the .svg in WordPress was a separate issue. It's not that WordPress wouldn't let me post the .svg, it's that I couldn't use its built-in image uploader to put it up on the site -- I had to use FTP. Here is the .svg at 100 x 100 pixels. Am told this will work in Chrome as well as Firefox (thanks timb); I knew IE just shows the image un-animated. Not sure about Safari or other browsers.
Update 2: Viewable in Safari, per asdf (thanks)