A hotfix is available from Microsoft to remedy the slow charting
problem in Excel 2007.
http://support.microsoft.com/kb/938538/en-us

Unfortunately, you can't download it directly yet and instead have to
call Microsoft support. I think they said it would be rolled out
officially in the first service pack for Office 2007.

But, if you explain your problem (slow charting) and reference the
knowledge base article as the solution, they will email you the hotfix
and not charge you the outrageous support call cost.

I've installed the hotfix on my computer and although charting is not
as fast as in previous versions, it is much, much, much better and
makes Excel actually usable as an analysis tool.

Cheers!