We came across this really helpful resource on codex.wordpress.org which tells you how to fix up your WordPress theme, and make it Widget ready. Widgets are now a standard part of the WordPress install so to reach the broadest audience all modern themes should support them, as well as supporting old style sidebars.
You need to know PHP, HTML mark-up and CSS to benefit from this resource, but if you are in to writing your own WordPress themes, then you probably are up to speed with these anyway. If not you will need to be, so why not get cracking now and learn?