TiVoWeb is more than just a web server; it's an application server. Extending its functionality is as simple as dropping a module into the right directory.
One really great feature of TiVoWeb is the simplicity of adding more functionality. Think of this as "hacking the hack."
Every item you see on the main screen is actually linked to something called a module. If you meander over to /var/hack/tivoweb-tcl/modules on your TiVo, you should see itcl files, reminiscent of each of TiVoWeb's menu items: ui.itcl controls the User Interface, search.itcl administers requests to the Search page, and so on.
If you find a module that you want to load into TiVoWeb and run (unfortunately, there is no master list, so you'll just have to keep an eye on bulletin boards like http://www.tivocommunity.com), just drop the file into the /var/hack/tivoweb-tcl/modules directory and select Restart → Quick Reload from TiVoWeb's main screen. This asks TiVoWeb to restart and load any new modules. Once that's done, you'll see any new menu item associated with the module among TiVoWeb's menus.
Personally, I really like the Now Playing with Sort and Folders and DisplayText modules, which we'll take a look at now.