For NES, Rampage is good for graphic hacking and basic text hacking (the font is in ASCII). Final Fantasy is good for graphics and some more advanced text hacking (it uses DTE). For SNES, Super Mario World as there are tons of tools for it. Super Mario Bros might be good if you want to look into coding as there is a complete disassembly available for that.

Tile Molester is the preferred graphics editor in the scene. For hex editors I use a mix of WindHex and Translhextion. Both have better features in different areas.

The Newbie Package of REQUIRED Material

ROMHacking.net FAQ: You ask, we answer!
ROMHacking.net Getting Started Section: Newbies Go HERE!
ROMHacking.net Documents Section!
How to ask questions the smart way.
On the Essence of ROM Hacking