The TourAlign Golf Alignment Sticks are a simple and cheap training aid that will improve your golf alignment drastically and which has other multiple uses, which include:
Feet and ball alignment by laying on ground for shoulders and feet.
Swing plane (Vijay Singh does this) by sticking in ground on an angle
Stuck side by side in the ground for a gateway to hit through
To aim at the sick as it will glance of due to its flexibility.
Many Tour Pro players are carrying golf alignment sticks in their bags, such golf proffesionals incude Rory Mcilroy, Robert Karlsoon, Stewart Cink, Paul Casey and Phil Mickelson.