for fontbook - first realize in osX - fonts are stored in multiple places.
The following instructions tell the locations of the various OSX system font directories and what you should do with each:
-Hard Drive/Library/Fonts - This location needs to be empty (if there are fonts in this location, you can delete them or move them to your own font folder)
-Hard Drive/User/Your User/Library/Fonts - This location needs to be empty (if there are fonts in this location, you can delete them or move them to your own font folder)
-Hard Drive/System/Library/Fonts - This location houses the OS X system fonts. The fonts that are installed to this folder by the OS are:
-Apple LiGothic Medium.dfont
-AppleGothic.dfont
-AquaKanaBold.otf
-AquaKanaRegular.otf
-Courier.dfont
-Geneva.dfont
-Hei.dfont
-Helvetica.dfont
-LastResort.dfont
-LucidaGrande.dfont
-Monaco.dfont
-Symbol.dfont
-Various Chinese Fonts
** keep all these fonts here - you may not be able to boot up if they're removed**
**ALSO KEEP ANY FONT HERE YOU WANT ON ALL THE TIME**
-Hard Drive/System Folder/Fonts - This should only contain the five fonts needed to run Classic (if there are other fonts in this location, you can delete them or move them to your own font folder):
Charcoal
Chicago
Geneva
Monaco
New York
You'll notice in the attachment i posted that each of those font locations listed above are icons in fontbook.
I keep all the fonts that I want loaded all the time in the SYSTEM.
Make a new folder on your drive for your project "POSTER FONTS" or whatever. when you drag that folder to the far left window of font book it creates a set called "POSTER FONTS" and turns them on automatically.
When you want to turn the set "POSTER FONTS" off - right click and go to disable.
You will see any set that you add - the fonts will show up under USER instead of SYSTEM.
You sometimes have to quit and relaunch a program when activating / deactivating fonts.
Suitcase is very similar and may have some benefits but if you are running osX then fontbook is already on your computer (free).
GOOD LUCK!