Either engine oil cooler lines, or transmission oil cooler lines. Fix either one right now as catastrophic damage to the power train item it's cooling will be guaranteed.
Check your oil. If it's low, that's the leak. Get it fixed ASAP. If it's trans fluid, same thing, fix it ASAP.
Also, trans fluid is a red color. Oil (obviously) would be more of a black/dark brown color. If it's leaking trans fluid, it will burn up the transmission if you let the level get too low. (if you have an automatic, that is) If the fluid smells burnt, it's probably trans fluid.
1996 Ranger 3.0, 5 speed stick, 4x4, 3.73's, 31" BFG AT KO's
Wiring, it's all fun and games until you poke yer eye out with a soldering iron...