Why use Excel?
Excel is the world's leading spreasheet package.
It is a very powerful program, that can be customised to meet specific needs.
Given that it is a key part of Microsoft's (so far successful) plan to take over the world, it is likely to be around for sometime.
If you use Excel already you may want to see how it can be used more efficiently.
Links:
Far and away the best Excel site is John Walkenbach' spreadsheet site. From his links page, you can get to every major Excel site on the web.