DAEMON Tools for Mac
Excellent virtual CD/DVD drive emulator
Let's face it, if you keep loads of applications open, whatever processor and memory your Mac has, you're going to be facing slowdowns. What Bokeh aims to do is refocus power to those applications that matter.
The application comes as a drop down menu bar item, from which you can select applications to pause or simply set which one to focus on. This last action allows you to simply pause all other applications except the one you will use. You'll see your screen flash for a split second and then blur out, except for the selected application. While I found that pretty cool at first, it really makes you dizzy after a while.
Bokeh works with as many applications as you want and it's nice being able to select which ones to freeze without having to shut them down. However I did find that Bokeh used up a lot of memory, generally more than 100 MB, and turning Activity Monitor also revealed that frozen applications still used up as much memory as if they were running.
If the focus effect doesn't give you headaches, you might using Bokeh. Yet don't expect it to free up loads of memory for you. For that try Onyx.