Long Hill Runs build slow-twitch endurance by incorporating from half a mile to 2 or 3 miles of steep hills into your long run every 2nd or 3rd week.
Long Hill Repeats strengthen intermediate fibers by running 4-8 30 second reps to start and working up to 90 second repeats.
Short Hill Repeats strengthen fast twitch fibers with 30-60 yard repeats (about 8-10 seconds) at just under an all out sprint.
Hill Springing & Bounding builds strength and improves stride on a moderate grade by doing 2-3 rep form drills. I definitely recommend watching the video to see what your form should be.
Downhill Strides put a lot of stress on your quadriceps and make them stronger, and you should never do more than a few in any session.