Hide any program even from the taskbar, minimize to tray, and more, with Process Manager
Process Manager is a free program making possible some useful operations you can perform on a process.
The program lets you have each of your open programs Always on top, hide it from the task bar and the Alt+Tab sequence (to reveal it you can use the Process Manager system tray icon); Hide all programs except the one you just clicked.
Other useful commands are to minimize any application to the system tray; Change the transparency level of a program’s window; Increase or decrease on the fly the priority a program’s priority.
If these is more than you need, the program lets you also customize it, limit the options that are available when you right click a process.
Process manager is a nice freeware you may like to use if you consider yourself a power user, needing more control over your working environment.