Personally I tend to encourage people to read Bogleheads' Guide to Investing first. That should equip you with everything you need in order to get your feet wet.
Then, while you're checking your investments every day (exactly the way the book tells you not to do), start to read as much as you can about Permanent Portfolio. The reason I recommend this is because it allows you to learn the theory of (and indeed watch, if you decide to build your own Permanent Portfolio) different asset classes, and how they move depending on various macroeconomic factors.
Finally, if you want to start stock picking I'd recommend getting started with Peter Lynch's books.
Intelligent Investor is good too as per other commenter but I find that it's quite hard reading for a beginner.
"The four pillars of investing" "The intelligent asset allocator" - more technical
The Boglehead wiki is also fantastic.
The reddit personal finance sub forum, read the sidebar
Boglheads.org
A random walk down wall street by Malkiel
Those three resources will be sufficient to put you ahead for retirement investing without being ripped off.
Calm, mature advice for investing that has stayed true for over 50 years.
* the smartest investment book you'll ever read
* the four pillars of investing
* The Millionaire Next Door
* If You Can