Finally a multi-monitor utility that works for me. And it's written in .NET and works on Vista x64 just fine. DisplayFusion sits in your system tray and does two things very well. It allows me to switch windows between screens and resize them as well at the touch of a windows shortcut (Win-Right Arrow for me) and it manages desktop wallpaper across unevenly sized monitors. I can even load a photo in from Flickr if I so choose.
This little app has only been around since August, but it's definitely worth some love if you work across many monitors.