After months of procrastination and searching about, I finally found out how to export my photos to an HTML slideshow from iPhoto and have it work the way I wanted it to. BetterHTMLExport is a shareware plugin ($20) for iPhoto 2.0 that lets you control image sizes, thumbnail sizes, balance image quality & file size, and output into your own HTML templates. The plugin comes with its own little language (with ifs and loops) that you can use to display any information that iPhoto stores about an image, set variables, and conditionally display or hide certain chunks of code. Pretty powerful and worth the $20. See my Paris photos for an example of the output.
My only complaint is that the filenames can't be modified (although the HTML file extensions can be...to .shtml or .php for example). I'd love it if the image names weren't 1.jpg, 2.jpg..., but something like louvre.jpg or 20021106louvre.jpg instead, similar to how Adobe ImageReady handles filenames when exporting web files.
Update (1/18/04): The latest version of BetterHTMLExport (2.0.10) works with iPhoto 4.