This is a simple little mod I made that adds jetpacks into Minecraft. They aren't particularly easy to get, but once you have them, they're super useful. This was my second mod, so no hate please. It's still a work in progress (By the way, my first mod was a tiny little creative enderpearls thing)
WARNING! This mod has not been tested in SMP! I assume that it works, but it's completely possible that it does not. Just a warning, on your own head be it if you fly into the air and your buddy goes too (even though he's not pushing the button).
Combining Jetpacks w/ Armor:
(this applies for all vanilla chestplates)
Press L-ALT to fly up (by default)
Press L-CTRL to toggle hover mode (vertical movement is stopped, horizontal still works.)
(Note: This mod is long since beyond development. I am mainly uploading it here for two reasons: for one, I am changing websites and don't want the old files cluttering my site up, and for two, someone might actually use it here. Please do not submit feature requests, bug reports, etc., as they will not be responded to.)