Over the last couple of evenings, I created my first-ever WordPress plug-in, which I wrote to make it easier to customize the WordPress registration (and login) screen. As distributed, the stock version of WordPress uses a really not-very-nice registration screen--it features the WordPress logo (embedded in a background image), and links back to the WordPress site. If you wish to modify the login screen, you have to change some files in the WordPress core--and that means that every time you update, you have to remember to redo those customizations. Far from ideal...
So I took some time to read about creating WordPress plug-ins, then studied up on the available hooks to see if what I wanted to do was possible. The good news is that, as of WordPress 2.1, it was possible--and quite simple (even for my very-limited PHP skills).
After a few error-filled attempts, I wound up with a working plug-in that creates a nicely-customized registration screen, all without changing any core WordPress code--you can see the results on the registration page. (This is roughly what it looked like under WordPress 2.0, but I created that page by modifying the core WordPress files.)
If anyone wants this plug-in, feel free to grab it (36KB download)--there are some basic instructions in the customreg.php file, but I wouldn't describe it as heavily documented. Also, I'm not sure how well it works with the default login screen, as I use the King Login sidebar widget for login in the sidebar. What I'd really like to do is figure out how to display the registration form with the header, sidebar, and footer--but after some basic investigation, I think that project is beyond my skills. So for now, this is officially good enough.