(Not to be confused with the similarly named, but infinitely awexomer, Infinite Jumping Glitch)
Press and hold your Jetpack button. While the jetpack is still firing, press the iPad/iPhone's power button to turn off the device. With the v1 jetpack you have to be quick, it's a little easier with the better jetpacks. You'll know it worked if you are still hearing the jetpack sound (briefly) after the screen goes black.
Now turn your device back on. You are now Hopping!
While Hopping, you can do anything you normally do in the game: move around, place blocks, drill, pick up items, throw away items, use the Assembler, etc. -- anything that doesn't involve pressing the Jetpack button. You can climb only one block at a time, so you might need to choose a path carefully in order to go up a hill.
Placing blocks and drilling are somewhat challenging in Hopping mode.