Here is another method that has frozen/fixed top & bottom rows, and frozen left and right columns.
Unlike the above solution, it does not dynamically alter the CSS, because I think that technique is likely to be unreliable. It also doesn't need the scrollbar mouseover hack which is a definite improvement.
The new code is fast in IE, and fast enough in Firefox and Safari (tested with 50 rows and 15 columns).
There is no jitter, and like the previous solution it uses NO IE expression: in the CSS (expressions cause serious unobvious lag problems; especially with big dynamically generated pages when you use :hover psuedo-attributes in IE7)
I hope this is useful.