As far as websites go, then try the following:-
http://www.excel-center.com/
On-line Tutorial - Probably best starting here
http://cpearson.com/
(Will take you a month of sundays to get through that lot)
http://j-walk.com/ss/excel/index.htm
John Walkenbach's website - say no more
http://www.contextures.com/tiptech.html
Debra Dalgleish has some great tips that will get you up and running with some
wizzy stuff straight away.
http://www.mvps.org/dmcritchie/excel/excel.htm
A compendium of stuff from Dave McRitchie.
http://www.tushar-mehta.com/
If Maths and Numbers are your forte, then this one is for you.
http://www.rondebruin.nl/
Some great bits from Ron, that I wouldn't be without now.
http://peltiertech.com/
Chart Stuff Galore, and a whole lot more.
http://66.206.3.208/Excel/Default.htm
Oodles of Goodies
http://www.jkp-ads.com/Download.htm
The only way to deal with names in Excel
http://www.mcgimpsey.com/excel/
Both Windows and Mac Magic with Excel
http://www.stfx.ca/people/bliengme/ExcelTips/
Excel Tips and Tricks
http://www.dicks-clicks.com/
Click and Explore
http://www.mrexcel.com/
Nice resource for a whole bunch of Excel stuff
That little lot should take you about 20 years to get through.