Heraldry, the study of coats of arms, crest, &c. is one of my favourite hobbies. Being a nationalist, I have posted on this site as much Canadian heraldry as I could find (except for personal heraldry, of which there is way too much to fit on my webspace. I'd be too tempted to abate the arms of certain hated politicians anyway).

National Flag, Coat of Arms, and even Tartans.

Provincial and Civic Heraldry, in sections-
British Columbia
The Prairie Provinces
Ontario
Quebec
The Atlantic Provinces
The North

Academic Heraldry

The Royal Heraldry Society of Canada. The Prairie Branch of the RHSC publishes The Prairie Tressure (issue one available).

Meetup.com is a good way to meet other heraldists in your area.

The Governor General's site on Canadian Heraldry
(includes instructions on obtaining your own arms!)

The Canadian Armorial (CHA grants from 1992 to 1995)

HeraldicAmerica (actually about North American heraldy, not the USA)

Try the Heraldry Quiz!

Heraldry's Most Frequently Asked Questions

Heraldica (Everything you wanted to know about heraldry, by F. Velde)

English and Welsh Civic Heraldry

International Civic Arms, and the complete list of Dutch Flags

The Baronage Webpage, with some good comments on heraldry and British traditions.

Hereditary Titles, with much British Royal Heraldry.

The British Heraldry Society

The Scottish Heraldry Society

Heraldry Australia

The Scandinavian Heraldry Society

The American Heraldry Society

Some Ukrainian Heraldry

And, since I am the Mad Alchemist, here's some alchemy-related heraldry!

The ultimate list of flag sites.

And for those who think they know their flags - Name That Flag!! (I won!! Finally!)

The dragon seen in the background is a detail from a woodcut done by my great-grandpa many years ago. If I ever become rich enough to register my own coat of arms, this drake will be the crest.