An excellent market research database. You can find everything from magazines to publishers for your stories. Gives information on how long the market has been around, payscales, and feedback from users on reliability of the market.
A wonderful forum where writers of all levels of skill meet to discuss writing. Great resource for critiques and valuable industry information.
By far one of the most useful sites for writers out there. They have done the research on so many publishers, agents, and markets to make it a safer world for writers out there. Have questions, they just might have the answer. I would bookmark them.
The good folks of SFWA have put together a virtual cornucopia of valuable information to educate and protect new (and even experienced) writers out there. Again, bookmark this one.
There are so many useful and immeasurably valuable sites out there, but this is still one of my favorites. Take one look, and you'll see why.