Stick the footer where it should be.. the bottom of the page
Sometimes things that used to be really simple with tables can still appear pretty hard with CSS. This layout for instance would consist of 3 cells; two with a fixed height, and a third one in the center filling up the remaining space. Using CSS, however, you have to take a different approach.
Min-height
The #container element of this page has a min-height of 100%. That way, if the content requires more height than the viewport provides, the height of #content forces #container to become longer as well. Possible columns in #content can then be visualised with a background image on #container; divs are not table cells, and you don't need (or want) the fysical elements to create such a visual effect. If you're not yet convinced; think wobbly lines and gradients instead of straight lines and simple color schemes.
Relative positioning
Because #container has a relative position, #footer will always remain at its bottom; since the min-height mentioned above does not prevent #container from scaling, this will work even if (or rather especially when) #content forces #container to become longer.
Padding-bottom
Since it is no longer in the normal flow, padding-bottom of #content now provides the space for the absolute #footer. This padding is included in the scrolled height by default, so that the footer will never overlap the above content.
Scale the text size a bit or resize your browser window to test this layout.