Cheap-O (the sub $2 magnetic endstop)
by hmeyer, published
This is the simplified DIY version of a magnetic endstop. Instead of using a hall effect sensor and some logic, it uses a hall switch. So the board is much simpler.
PLUS - it has a control LED.
Cheap-O in action: http://www.youtube.com/watch?v=smRay_nAUWA
Update: Improved STL for super slim design.
Get a TLE4905 (for about 1 EUR), 2 x 4.7 nF caps, a LED, 1.2kOhm and 3.3kOhm resistors and a tiny piece of strip board pcb (I needed 7 strips by 5 holes).
Drill 2 3 mm holes.
Solder according to photos and schematic.
Glue a magnet to your axis (I used 3 mm neodym cubes).
enjoy your cheap and accurate endstop.