So, for WordPress users, here's a plug-in that seems a notch above the rest, for writing PHP inside posts without some of the problems accompanying other plug-ins.
An example of how this could liven up your site: With Flash, you can make images more exciting by animating them, but that's a lot of work. With this plug-in, you can still make them more interesting by making them dynamic in other ways; for example, filling a space with a random image from a bank of images you've compiled, to keep things fresh. Since PHP drives a lot of this kind of action, anything that makes it play nice with WP is helpful. Even if you don't plan to learn PHP, you can hire someone to write and install the script, so all you need are images, or whatever you want to make more dynamic.
Keep in mind that this is not stuff in which I am very experienced. If readers spot anything misleading, please post a comment with a correction. And, as with any software mentioned by some guy you don't know, do a little background research to check my own before installing anything.
If you do something interesting with this plug-in, I'd love to see it.
Note: After posting, a dissenting comment arrived below, which you should read, as it warns of security issues that I cannot evaluate at this time.