Use old Powerbook G4's screen
Yes, but it's not worth it.

The screen in that iBook is basically worthless: it's a small, not very good screen. You're better off spending any money on a slightly better display that–if nothing else–is larger.

However, if you really feel like it, you can do so.

First, you'll need to identify what display you have. Run the command ioreg -lw0 | grep IODisplayEDID | sed "/[^&lt;]*&lt;/s///" | xxd -p -r | strings -6. This will output two strings. Copy the first one which should look something like "LP133WX2-TLC1", then search it. This will show you what panel it has. Using that info, search for it's controller. Using the same example here's a VGA controller for that panel.  This will allow you to  use it as a monitor.

Again, let me reiterate: this probably isn't worth it for that panel. You can get a larger, nicer panel for the same amount of money and time you'll invest. But if you feel like doing it, go ahead.