... or rather, thinking beyond the tables.
Over and over again I see the same questions crop up on a stylesheets listserv of which I'm a member. Most of the time it revolves around taking a tables-based layout and redoing it as a stylesheets layout. Most of the time it's a fairly straight-forward exercise. Sometimes the layout is quite complex - like the photoshop comps that we used to slice into table layouts - and that is when you need to think beyond the limitations of tables.
When you first transition from tables-based website layouts to stylesheets, there seems to be a huge shift in conceptualizing how to build the new designs. Most dramatic is the added dimension of depth. I'm not referring only to the z-index attribute but more to the concept of onion-skinning layers of presentation. Maybe you could think of it as the "Planes of Presentation" where building a website with CSS is more a concept exercise of layering various transparent planes containing bits of the overall presentation. The final product is then the overall view down through all the layers.
Getting to the point where you can free your mind from the limits of tables and being able to think in more spatial terms seems to be the major hurdle to overcome. But, once you're there the design possibilities are truly endless. Really they are - just visit the ZenGarden official designs site and see some outstanding examples of the same content presented with vastly different styles.