Introduction to jQuery UI
jQuery UI lets you build a lot of cool elements with minimal work. Things like dropdown menus and date pickers (and much more!). See http://jqueryui.com/ for more. You can 'roll your own' theme, or pick from thousands of premade ones. http://jqueryui.com/themeroller/ (A theme is like a color scheme). Some examples below.
jQuery UI is a separate library that works with jQuery. To include it, add the following lines to the head of your page AFTER you include jQuery:
Check out my GIANT slider!
Date Picker: http://jqueryui.com/demos/datepicker/