I've just completed putting together a jQuery plugin that will take valid single table using valid html (have to have a thead and tbody) and will output a table that has fixed headers, optional fixed footer that can either be a cloned header or any content you chose (pagination etc). If you want to take advantage of larger monitors it will also resize the table when the browser is resized. Another added feature is being able to side scroll if the table columns can not all fit in view.
http://fixedheadertable.mmalek.com/
It's extremely easy to setup and you can create your own custom styles for it. Also uses rounded corners in all browsers. Keep in mind i just released it so its still technically beta and there are very few minor issues i'm ironing out.
works in IE6, IE7, IE8, Safari, FireFox and chrome.