When searching for simple emergency kits, we came across Equipped to Survive, which has some tips on building a very basic, affordable kit, although it's very text-heavy. We like how they prioritize and thoroughly explain what you need. eHow.com also has some pretty user-friendly articles, lists, and videos. And of course 72hours.org is helpful but pretty daunting.
Below, we've included a couple of basic lists that can help get you started with the necessities, so you can hopefully add other helpful stuff later. It's also a good idea to add spirits to your kit, if you partake, as well as books, cards, and anything else to pass the time.
Additionally, any well-prepared DIY folks out there are encouraged to provide advice to all of us procrastinators in the comments!