Though I prefer systems programming to web development, I've still had a lot of fun (ab)using radio & checkbox <input>s with CSS. For a cleaner source, <label>s can be used to separate "buttons" from their actions. While carousels can be entirely done with HTML & CSS, they are well complemented by small amounts of JS. Also, as long as you don't try to do anything too fancy, carousels can easily be done without keyframes.