Recently I tried to find an online tool to resize an image map. Not the image itself, that's easy, and there are already lots of such tools. But to regenerate all the coordinate information for the image map.
If you want to dynamically resize an image in a web application, along with its image map coordinate information, the code could be used with few changes to do that as well. This would have the effect of the client's browser performing the scaling, which is usually not preferable to creating the source in the size you want, but in some situations could be necessary.
The general idea of using jQuery on blogger also opens lots of possiblities... you could do almost anything you wanted by cleverly manipulating the resources on blogger, I would imagine up to and including ajax. For example, Blogger lets you have ten "pages" of static information in addition to blog posts. You could use one of them as a content placeholder, and use jQuery to get specific content out of it using ajax, to get around that limit. Or use it to make substantial changes to the page layout.