My Subaru won't start without a jump. the battery is new and she still runs if the battery is disconnected, leading me to thing it's something other than the alternator. once started everything runs great but after I turn it off it won't start again unless it's jumped.

This procedure usually works:
·Check the battery cable connections:
Make sure the positive cable, makes a good connection at the battery and at the starter. Make sure the negative cable makes a good ground connection at the battery and (preferably) at the engine.

·Check the battery the simple way, like this:
Turn on the headlights, then try to start the car.If the headlights do not dim or go out, then the battery is likely ok.

·Check the starter and solenoid:
If the wiring looks ok, then look at the starter solenoid for a good connection, and proper voltage at the starter(10 volts minimum while cranking).
If the starter spins and no crank, the problem is most likely the Solenoid's bendix gear is stuck.
Have someone hit (not too hard) the starter while you try to start the car. This usually works by dislodging a stuck bendix gear.
·Make a simple test of the alternator:
If you can, somehow get the engine running, measure the voltage at the battery. It should be at least 13.6 volts to properly charge the battery.

On all cars built the last 25-30 years: Never, never pull your battery off when car is running: you can fry a bunch of electronics (computer, sensors, ignition circuits, alternator). Never pull battery off when key is on, either.

It sounds like you got a bunk batters that is not giving you enough cold cranking amps to start the engine. Take the battery to your local auto parts store and ask for a battery test to make sure. Some batteries can be bad right off the shelf. The other possibility is the alternator isn't putting out enough power to both run the car and charge the battery, I have seem that happen. The parts store can test your charging system as well, they should do both tests for free.

Check the starter and the starter connections. freyed\loose connections...

(especially any grounds at the starter or any large common grounds)