TransWindow

TransWindow is an application with the sole purpose of making all the windows on your computer semi-transparent, except when they're active.

Thanks to this effect, the other windows in the background will be much less distracting, which is especially helpful if they include photos or other things that easily snap away your attention.

TransWindow is a fairly simple application. To use it, just double click on its executable drive, whereupon everything running behind your current window will become transparent.