Well, your best bet would be to pull out the electrical wiring diagrams for your year and model and start tracing to see if any fuseable links or fuses are gone. If you are getting no spark at all, it could be an open coil, bad ignitor, broken rotor/distributor, open pickup coil on the distributor, bad ignition switch?
1. Check the fuses first.
2. Measure the primary and secondary coil resistances of the ignition coil and make sure neither is open.
3. Take the distributor cap off and inspect the rotor.
4. Put it all back. You said you believe you see power to the ignitor with the ignition key on. Get someone to crank the engine and use a meter or your light (use a neon light I would think) on the output secondary of the ignition coil going to the distributor to see if it is firing. If it isn't, then it is something in the coil , ignitor or ECU. ECU may not be getting proper sigs from the distributor pickup coils.
5. If the ignition wires are fairly old, I would buy a new set along with a new rotor and dist. cap first to eliminate all those. Cheap to do and will improve reliability anyways.
Ignition Manual:
http://www.camrymanuals.com/manuals/90/Ignition.pdf
Dave Mc