The Slash theme is originally from Slashcode. I found a version for PHP-Nuke that I later converted to Postnuke and now to Drupal. I would call it a retro theme, it's certainly not modern or fancy.
The main style is dark red and there are additional styles that are, black, blue (MacSlash) and green (Slashdot). Tables are used for the three column layout, the main header and the header for nodes and boxes. For the rest CSS is used.