We built this one to be used with TeleToyland, and you can try it out live at the TeleToyland Marble Maze, and a second bigger one, the TeleToyland Marble Maze 2.
To make setting up and changing the maze easy, we used a Lego plate and bricks.
Step 1: Materials
Metal - for the following, we used about 5 feet of each:
1" wide x 1/8" thick aluminum bar for the X axis
1 1/2" wide 1/8" thick aluminum bar for the Y axis
1 1/2" wide by 1/16" Aluminum angle
1x4 pine for the base - need about 34"
#6 nuts/bolts - a few lengths, a couple 1" ones, and the rest 3/4 and 0.5 inches long
#6 washers and #6 split lock washers
We used Hitec HS-625MG servos. Even though the mechanism is well balanced, standard hobby servos tended to jitter a bit. Note that for TeleToyland, we also turn the servos off when they are not moving.