Samsung has done a pretty great job with multiwindow on the Note lineup, however you can only take advantage of a few apps with the multiwindow feature. Mostly you get access to touchwiz apps only in multiwindow. If you don't have a Galaxy device you are pretty much left out of the multiwindow fun since no other OEM has really adopted multiwindow. The "Multitasking" app changes all of this! With Multitasking you get true PC like multitasking with the ability to open up several windows on the same screen. Who doesn't want to watch a movie while working! Windows can be resized, you can move them anywhere on the screen, you can use the windows in fullscreen mode, and you can minimize the windows into the notification bar. There are both free and pro versions of this app. The pro version is adfree and includes more features and more tools. The Pro version is only $2.07. Head to the play link below for the download.
Also note, that this does not "window" apps already installed, but rather puts pieces of the developers apps into windows. For example, he has a browser, a note taking app, and a calculator that he bundles with this app. These apps are resizable, and "windowed", not your apps.
I've installed this app twice now and uninstalled twice. Last time I uninstalled it because of the massive battery drains I was getting without even running the app. Tried it again when I saw this thread and noticed it had already used 25% of my battery while only having it installed for 2 hours and only using it for 2 minutes.
Looks alot nicer than last time I had it, but the battery drainage keeps me from using it. Once they fix that, I'll give it another shot.