Can I speed up the auto-dismissal of Notification Center banners?
Although I never usually have any luck finding them, I used MacWorld's guide, "How to find hidden preference settings", and I was able to find the hidden preference:

defaults write com.apple.notificationcenterui bannerTime &lt;SECONDS&gt;


Type the above into Terminal, replacing &lt;seconds&gt; with the number of seconds you want the banner to last for, and press return. Then, log out and log back in to reload Notification Center.