Okay, so you wish to make a development/flash cart. First, you need to find boards that offer maximum compatibility with games. Games with special chips generally aren't worth modifying because only one or two games use them. Otherwise, SA-1, SDD-1, SPC-7110 and Super FX+FX2 carts use surface mounted ROMs or 16-bit ROMs.
Normal games use two types of boards, LoROM and HiROM. Any board you use should be able to accomodate 36-pin ROMs, and most do for 4 Megabyte and larger games. So you need two boards. I recommend using Mario Paint for LoROM games because it has a 32KB S-RAM. A few other LoROM games also use this RAM size. The cartridge can be had cheaply as it is abundant.
As for HiROM games, many RPGs will do but they are expensive. I therefore suggest something like Ken Griffey's Winning Run. It has 8KB of battery backed S-RAM (I know of no HiROM game to use more) and has a 4MB ROM (no extra wiring to the address decoder.) As it is a sports game its not too difficult to find.
Normal games use two types of boards, LoROM and HiROM. Any board you use should be able to accomodate 36-pin ROMs, and most do for 4 Megabyte and larger games. So you need two boards. I recommend using Mario Paint for LoROM games because it has a 32KB S-RAM. A few other LoROM games also use this RAM size. The cartridge can be had cheaply as it is abundant.
As for HiROM games, many RPGs will do but they are expensive. I therefore suggest something like Ken Griffey's Winning Run. It has 8KB of battery backed S-RAM (I know of no HiROM game to use more) and has a 4MB ROM (no extra wiring to the address decoder.) As it is a sports game its not too difficult to find.