Are you looking to make your own templates, or use ones that were already developed by someone else? You can make your own components just fine with Template Toolkit, and you can easily insert other widgets you find into Template files.
I don't know of any ready-made packages that you can just download for common things that show up on web pages. It would be nice if someone spent the time to create some and make them available. I think people tend to make their own stuff that is exactly right for their problem, isn't necessarily refactored or well-architected, or a bit kludgey and embarrassing.
I have my own bits, such as templates for a country or state selection menu, but I also have to have some code to set the default. I don't particularly want to spend the time to make that useful to a general audience.
I understand what you want, agree with the value of it, and hope someone with the talent, time, and motivation runs with the idea. :)