What you can do is go into Macintosh HD > Applications > Adobe After Effects CS5.5 > Presets. Make a new folder in there named "My Favorites" and then create subfolders within this if you need to. Create copies of the presets that you want in there by Option-dragging them from the original folders. You can also save your own custom presets into here from within After Effects by going to Animation menu > Save Animation Preset. Please note that you can't preview any of your custom presets in Bridge but you'll be ale to see your new folder structure and the presets contained next time you restart AE.
Hope this helps!
Angie Taylor animation & illustration for television, film, web and devices