Q: Is there an organizer application for iPhone/iPod touch applications so that I can organize the apps into categories rather than just dragging them between screens? Also, incidentally, is there a limit to the number of apps an iPhone will hold (space considerations being understood)?
A: Unfortunately, at this time there are no official applications available through the iTunes App Store that can do this. The iPhone SDK does not permit applications to modify the layout of the main iPhone or iPod touch home screens, so you are pretty much stuck with what Apple gives you in this regard.
Note that if you are willing to “jailbreak” your iPhone or iPod touch, there are a number of unofficial third-party applications that may provide more options in this area. Note that these unofficial applications are not in any way supported, tested or certified by Apple and care should therefore be exercised before installing or using such applications.
As for the maximum number of applications that can be installed on the iPhone, you are basically limited only by the number of home screen panels available, which is 9. With 16 applications per home screen (including the built-in applications), plus the four apps in the dock, this provides a maximum of 148 applications which can be accessed from the device.