By ticking the Auto-hide the taskbar checkbox in the taskbar properties you can make the taskbar hide itself if you don't hover your mouse over it's position - this gives you a bit of extra space, especially for wide screens.
One problem you might have though is that the slide animation is quite slow and there is no registry key for speeding things up. One thing you can do however is to switch off the animation completely so that the menu hides and reappears instantly. To do so,
- go to Control Panel > System and Security > System > Advanced System Settings > Advanced (tab) > Performance Settings... > Visual Effects (tab)
- Uncheck Fade or slide menus into view
- Apply changes