Thanks guys, yeah, I'm going to make another later today and I'll note all the dimensions.
-A Game Boy cartridge
is 56.8mm wide -The upper rods are ~58mm apart, measured center to center.
-The lower rods are 30mm apart, center to center. (Edit: 35mm would better support the games on the bottom)
-The end pieces don't matter so much and can really be anything that you want as long as the dowel rods are in the right place, I will make them a bit smaller for the next one.
Edit: This is a pretty simple project but here is probably the most helpful bit. The length of the dowel rods don't so much matter, they can scale to any size you need. When done drilling, there should be NO material removed from the inside of the vertical lines.
55mm is the most important. The actual distance in between the inside edge of each dowel rod is 57.5mm which fits *perfectly*. I'd shoot for 58mm or you may have to sand/whittle some material away down the whole length of the dowel rod, a mistake I made on the second one I made today. 55mm is too tight.
46 mm isn't really important, it's just what it turned out to be after I eyeballed it. I didn't drill through the endpieces for the dowel rods either, I just started a hole and then press fit the dowel rods in along with a bit of wood glue.
[img width=700 height=394]http://oi62.tinypic.com/fctzjm.jpg[/img]