Parking brakes generally don't stick suddenly.

Stuck master cylinder (happened to me). To release you have to know whether its the front or back brake lines (try jacking up the car and turning the wheels like the others have said). Upon finding the correct line, release the brake pressure by backing off one of the brake fluid line nuts near the master cylinder. Have some towels nearby to catch that nasty brake fluid. If its the brakes you should be able to feel or hear some groaning from the brakes.

If the wheels all turn easily, its the automatic transmission. B2 piston problem.

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84 300DT Puke Yellow. Totalled after 438,000
84 300DT Orient Red. 169,000 (actual mileage may vary)
2002 Explorer EB (wife's)