Lots of sites I design require either message alerts to get the user's attention, or animated forms that slide into place. I use to code these one-by-one with jQuery but that's time consuming. Now I can often just use one cool jQuery plugin, Reveal, to handle all these needs within a site.

Reveal is easy to use. Just add a tiny JavaScript to your site,  a few lines of CSS to your stylesheet, and create the HTML that will hold your popup messages or forms. They will stay hidden until a user clicks a button or link, or you can have your own code cause a popup to appear when a user changes a form field or hovers something on the page. Then the Reveal window, instead of popping up, will animate in from the top of the screen, dimming the background of your web page to focus user's attention. When the user clicks anywhere on the page or on the close button, Reveal animates the window off the screen.  There are  demos on the Reveal website.

Learn more about Reveal