Andreas Verhoeven has released three really great Windows Vista tweaking applications, designed to improve some of the visual decisions Microsoft made in Vista without much effort on your part. Download them and load shortcuts to them into your startup folder (only one of them will do it for you) and you should really enjoy the results.
Glass Toasts replaces the balloons that come out of your system tray with something a bit more ostentatious, a glass balloon that is too flashy for most users. Then again, that is probably the point.
3D User Picture takes the picture that appears atop the Start Menu, makes it 3D, and has it rotate. This means that your user picture, plus all the icons in the Start Menu that go up there when you select them, all get this cool effect, and the effect only uses system resources when the Start Menu is open (so there's little cost to actual use of the computer.
Thumbnail Sizer lets you dramatically increase the size of the taskbar preview thumbnails, increasing seperately the height or the width (so if you want wider, but not necessarily taller, that's easy). You can even slow down the fade in/out animation so you can enjoy that more.