Archinect is a useful place to look for information on the practice of architecture and the people who do it. It is also the best site I know of to look for architecture and interior architecture jobs. If you are a student, it is a good spot to rove around in and get a sense of the options available to you once you graduate.
A good source for contemporary precedents and examples, materials and how they are used in design, plus news about the industry, competitions, prizes, etc.
If you want a sense of the profession, the markets for illustration, and links to illustrators and agents, plus info on events, check out the Association of Illustrators. It's based in London, so gives US illustrators a sense of the global nature of illustration work.
The Society of Childrens' Book Authors and Illustrators is an LA based international organization that is the go-to place to start and build a career in children's book illustration. It will help you learn the industry, connect with other illustrators, editors, publishers, and more. I am a member, and have found it extremely worthwhile.