With javascript, you can get the screen size and/or window size pretty easily. Ive seen sites that resize the browser to the screen size and move the window to the top left corner so it fits the full screen. Something like:
<script language="javascript">
self.resizeTo(screen.availWidth, screen.availHeight);
self.moveTo(0,0);
</script>
Note: "screen.availWidth/screen.availHeight" takes into accout the Taskbar. "screen.width/screen.height" doesn't.