http://cheats.gbatemp.net/ They update every now and then. Go to the Forums (click the Forum tab) where they manually post cheats for individual games if they haven't been added to the databases.
what should we choose at that website for R4?? there are so many of the cheat data in that website...
Read the Help file available there. It will tell you what databases go with what cards. http://cheats.gbatemp.net/files/Credits%20and%20Help.txt
the R4 isn't compatible with GBAtemps database unless you patch this one system file, move all the games you need to the top with Yasu's R4CCE, or switch to YSMenu