Where do I start to learn about investments and retirement planning?

Is there a good website with explanations on terms such as mutual fund, bonds, equities…that also explains how to get started? I need help understanding person finance and investments. Any useful advice appreciated.
Personal finance, I meant!

I always like wikipedia

also check out scottrade.com they usually have good tips and are known by many to be the cheapest* method.

*They basically charge a $7 flat rate to buy and sell with no annual rates or commision profits. I have used them for years with no problems.