Baycon Group offers free tutorials for Excel 2007 and Excel 2003/2002. The tutorials display clear visuals and explanations on how to navigate and create an Excel spreadsheet. They also give you practice exercises to give you hands-on experience.
If you're more of a visual learner, YouTube can provide excellent free video tutorials to get you started in learning to work in Excel. Just enter "free Excel tutorials" in the search box and select videos to review.
GFC LearnFree is a useful site to learn Excel. It offers a free tutorial for Excel 2003 and a free online class for Excel 2007. You can begin using the tutorial immediately and at your own pace without having to register, but you are required to register for the online class, as space is limited.