Sticky Footer

CSS Solution:
www.cssstickyfooter.com/
The least buggy css-only sticky footer I've found - just arrange your page.tpl accordingly, add the CSS, and it works!

JS Solution:
www.css-tricks.com/snippets/jquery/jquery-sticky-footer/
This one is for the times when you can't create the proper page structure but still need that footer stuck to the bottom of the page.

Imagemap Rollover

CSS Solution:
http://www.noobcube.com/tutorials/html-css/css-image-maps-a-beginners-gu...
I used this recently to create a map that would allow users to select different regions as taxonomy terms - it is a bit intensive to set up, but the hover tooltips make it worth the time.

JS Solution:
http://davidlynch.org/js/maphilight/docs/
For pin-point accuracy. (See 'A map of the USA').

Tooltips

CSS Solution:
http://www.kollermedia.at/archive/2008/03/24/easy-css-tooltip/
Implemented a sleeker-looking version of this tooltip after getting buggy JQuery tooltips on a JS-intensive page.

JS Solution:
http://code.drewwilson.com/entry/tiptip-jquery-plugin
Using JS lets you add in neat effects and transitions.