I'd like to put my GB/C games in cases too, but I'm not sure how I'd do that.
Ahh that's what I was wondering about the most. All the solutions I've seen require modifying the cases themselves (cutting the GBA holder).
Oh! Let me chime in here! There are two basic methods of casing GB/GBC games.
The first method is simple and easy. Open the case, put the GB/GBC game in the center (right on top of the DS cartridge holder and close it. It'll close. It'll bulge out just a wee little bit, but nothing major and the cases still look great on the shelf.
The second method is the preferred method - cutting the case. You've got two options here. Both options require that you cut out the bottom of the GBA Cartridge slot. It's an easy cut that can be done with a simple razor blade or xacto knife.
The second half is a bit more difficult. I recommend a dremel tool (or a cheap knock-off for about $25 at Walmart). You'll need to cut off the top part of the DS slot. There's the hard way to do this, which requires all kinds of twists and turns and is a lot more effort than it's worth

Then, there's the easy-easy method that I like.

And the final product looks like this

The cutting is more work than the smush-it-shut method, but either way, the outcome looks great, when you have all your games spined on the shelf...
