ROM hacking Documents
Dream Maze: Kigurumi no Daibouken (SFC) Font
This explains how the 12x16 font is stored in the original Japanese ROM.
DTE Support via 6502
This is an old document explaining how to add a DTE routine to the Famicom version of Ys 3.
NES Rom Expansion for Translations
Explains how to expand an NES ROM. There's also a few things you may want to consider. ASM knowledge will be required in most cases to be able to use the expanded space.
Font Tables.
These are useful for dumping text from games using the indicated text format.
EUC
Shift-JIS