GodMode9 Explorer by d0k3 is a full access file browser for the Nintendo 3DS console. It gives you access to your SD card, to the FAT partitions inside your SysNAND and EmuNAND and to basically anything else. Among other functionality you can copy, delete, rename files and create folders. You can find the source here.

Changes:

[new] PCX bitmap viewer
[new] Extracting data partition for DIFF files
[improved] Improved ticket.db parser, only output verified titlekeys / tickets
[improved] Revised font system, now allowing to switch font in runtime (1)
[improved] Improved handling for batch operations
[improved] Improved titlekey and NCCH seed extractor
[fixed] Compatibility with CIAs containing >= 256 contents
[fixed] No more crashes caused by malformed CIAs
[fixed] Detecting CDN/NUS downloads
[scripting] ntrboot detection via $[HAX] env var
[scripting] dirsel command (works like filesel)
[scripting] isdir and exist commands (useful with if)
[scripting] for command, also works recursively
[deprecated] XORpad drive and ncchinfo.bin XORpad generator (2)