Here is a bunch of usefull utilities to browse/check/edit your NDS and 3DS ROMs.

Our prods (by PsyKo):

CTR v1.11 Checks and displays all basic info from 3DS/NDS/DSi ROMs.

Gateway ROM Patcher v1.2 is a patching tool to export/import/clean/fix Gateway's header data from 3DS ROMs.

3DSXtractor v1.1 is an utility to extract encrypted NCCH/ExHeader/ExeFS/RomFS parts from 3DS ROMs.

Other apps:

Rom Tool (by 3DSGuy) Tool designed to check/manipulate CTR Cartridge Image (CCI) files.

3DSExplorer (by Elisherer) is a file browser supporting 3DS ROMs, saves, and various other CTR files.

NDSHeader (by Vinpire) is a header viewer/File Browser

NDS Top System (by coolhj) is a header viewer/ARM info/File Browser