Reading:
(dead site)
Old site for hi res Coptic photos went down. Looking for replacement
http://www.bibliacoptica.com/links/horner.html
Fantastic resource of both dialects of Coptic of the New Testament.
Dictionaries:
http://www.metalog.org/files/crum.html
There's really no other such resource that I've found for Coptic online.
Grammar:
http://www.metalog.org/files/Plumley.pdf
There's really nothing else really needed than this single PDF. It truly captures everything you need for understanding how Coptic works.
Coptic Fonts:
http://scripts.sil.org/SophiaNubian