Advanced photography links
A Darker view: http://darkerview.com/, an excellent astrophotography resource although so big it takes a bit of digging. Start with the sitemap. The astrophotography page is great particularly the page on CCD problems.
Gary Honis. http://dslrmodifications.com/ Another great astrophotographer. He is the man if you want to get your canon modified for astrophotography.
A nice intro to astrophotography and the types of frames that you need to capture for your astro processing software. http://www.pbase.com/dtreed/how_its_done
Old but a nice read. http://www.saratogaskies.com/articles/cookbook/
More astro: http://www.budgetastro.net/
CHDK. http://chdk.wikia.com/wiki/CHDK Home to the Canon Hack Development Kit, and alternate firmware for canon point and shoot cameras that lets you do just about anything you can imagine. The forum is full of information and many years of very smart people hacking cameras.
Magic Lantern. Originally spawned from CHDK this is the ultimate firmware update for your canon DSLR. Again the forum is full of fantastic information. Of course search before you ask.
Diglloyd. Some good filter graphs here, this is the link to the free articles.