Here are a few pointers to other Corsica-related information:
wrote a great detailed description of hiking on the GR20.
has nice photos and some pointers to to other resources.
Corsica on the Internet
has lots of miscellaneous information about Corsica.
has photos and pointers.
has a short description of GR20 and a few pointers.
offers more pointers.
my own home page
carries photos I took in 1994, not to mention "Back to Corsica", which you are looking at!
Let me know if you discover other interesting sites!