1998 Toyota Tacoma won't start. I've put in a new battery, starter, altenator, and relay. The motor will turn over but the truck won't start without being pushed. When it is push started, it will fire right up and run just fine. Any ideas??

Weird. It's possible that the fuel pump or circuit opening relay may be giving out and the jolt from being push started gets the pump going.
See if it has fuel pressure when it's failing to start. I've started many of them using a rubber hammer and bang on the bottom of the fuel tank. Easy quick diagnosis.
Same could be for ignition circuits too.