Other Ways To Go Multi-Cart

Karl Frank reminded me that long before the GBA Changer, people have been using flash carts to dump several games onto a single cartridge for easy Game Boy playing. Although these devices are often used for piracy, copying your legitimate games for more mobile play is a real application for these items. Lan-Kwei is one of many import websites with these tools available. The difference is that the flash kits cost $50-150 compared to $10 for the GBA Changer. I'd probably prefer a flash cart myself though.

A word of warning up front: You won't be able to copy the Prophecy savegames (one of the main reasons I bought such a kit) that way without hacking the rom first (so you can only copy between the copies, but not copy <=> original)...