So Stardock released a new program called ShadowFX. It puts shadows under windows. There are several different styles and people can make their own styles though there is only one that has been made by someone so far. It works on inactive windows too and people can make the shadows work on both inactive and active windows or just active windows. Color schemes are an option as well and there are few that come with it that give your windows a neon glow. However, so far shadows don't work on any custom themes and only the default theme. I'm not sure if shadows work on windowblinds skins but probably not since those have their own shadows and it would conflict with them. So far I haven't seen any slow down of windows like what you see with windowblinds. It would be interesting to see if we could get their shadows to work with custom themes.
Below is a screenshot of what one of the shadows looks like. Here's a link to ShadowFX if you want to try it out for yourself.