This page shows a homebrew vertical antenna based on the Pac-12 antenna design. The commercial version of this antenna is available by Pacific Antenna. I'm not sure of the design history, but I based almost all my construction on KA5DVS's design.
The reason I call mine a Pac-15 is that I made the bottom rod sections about 15" long rather than 12" as described in KA5VDS's design. The upper whip was about that long, so I figured I might as well make the antenna a little larger while not changing the packing requirements. I have no idea if this helps or degrades the antenna performance - in any case, I like the little antenna, and it certainly is fun to work the world on gear that you've made yourself. Other than that, I did nothing original and tried to copy the established design and instructions as much as possible.
Here are the components used for a 20m setup. At the top is a whip from Radio Shack. Next is a 20m loading coil, which serves as the mounting point for the whip. The bottom of the coil screws into a connector on a 1/4" aluminum rod. This rod joins a second, which is attached to the bottom feed connector. Below the feed connector another aluminum rod acts as a base support, pushed into the ground, a clamp mount or support tube.
Missing from the picture are the ground wires. I have sets of 4 radials made from speaker wire and an alligator clip. They attach to the coax connector and are laid out as nicely as space permits.