If you put in the Jetpack cheat (< > R1 R2 L1 L2 up down < >
you can fly to the top of the Emrald Isle hotel in Las Venturas, get the parachute and jump off. There's also a Parachute at the top of the tallest building n Los Santos (it is octagonal and light pink.) You can get to the top easily by walking in the front door.