UPDATED! Once More - FINALI just finished up editing quite a bit on the content end of the Joomla core code, and have ended up with a completely table-less Joomla site that validates XHTML Strict! I thought there would be someone interested in this, so I will share.
Validation :
http://validator.w3.org/check?uri=www.megaman-games.comTest Site :
http://www.megaman-games.com(Please excuse my site, its incomplete and alot of the CSS has yet to be added. I just started on it. For strict validation, set the validator to strict to override the transitional)The only files modified are in the com_content folder and a module - content.php, content.html.php and the last modified file is the login menu. To make things a bit cleaner and easier, I added a few extra CSS classes/id's in the coding so you can better control the look of the modified items.
This hack will also allow you to change the look of your frontpage quite a bit (also your content). Using the CSS, you can make it so the frontpage headlines, author names, creation date, section / category, etc appear the way Joomla normally handles them (use display: blockl in your CSS for each) or you can have it presented in one row as a modern site usually does (they are spans, all you need to do is add some padding between each).
CSS Additions .author
.category
.section
.createdate
.modifydate
.readmore
#navigation
There may be a few more. If so, you can view your source to find out what they are.
Before you use this, make sure you backup your existing files. Download the attached zip, upload and overwrite the original files, and add the new CSS. That's it. To get completely table-less, you will need to set each of your menus as flat lists. I also loaded my menu with -1 switch as well (the header appearance of the menu there is actually a placeholder / seperator).
Ex. mosLoadModules ('left', -1);
Feel free to browse the source CSS and code at the site I listed above as reference. I have a default Joomla 1.0.12 install with the Joomlatwork.com SEO patch installed. If you don't have the SEO patch installed, this is present in the content.php file and will probably mess with your site! You should download and use the patch anyways, it works wonders for SEO purposes.
Have questions, comments? Feel free to reply or pm me. Sorry I haven't finished my site yet to show off what this mod really can do, but you will get the idea if you use it.
One small update - I am still working on editing a bit of the core files and reordering some things, so at times you may come into a messy site. I know I should be using another test site but you know, space is valuable

FINAL UPDATE - Using more than one flat list menu caused validation to fail. To fix this, I edited the main menu module php code and removed the ID from each flat list menu and replaced it with a class. I have replaced the attachment with the final attachment. Go ahead, check the validation of the site above, view the source, and check it out now that I've put the CSS into it.