StatusScreenSaver - don't miss notifications while your screensaver is on
Status Screen Saver is extremely well-designed. It's technically a screensaver file itself, it just lets you choose which saver you want in its options menu. Other well-thought out features: apps with new updates have red badges, and they're grey if there's nothing new, the icons are resizable, and you can create your own AppleScript modules for apps that aren't already supported. The only very minor quibble we have is that badges get cut off a bit when you get into four-digit numbers, but you can work around this by not having 1100 unread emails.