Here are some sites I use/have used to help me build my craft. Feel free to leave your own suggested sites in the comments.
Free Writing Resources
Podcasts:
Writing Excuses
15 Minutes of delving into various topics related to genre fiction. Always ends with a writing prompt.
Hide and Create
30 Minute discussion of various aspects of genre fiction.
Grammar Girl's Quick and Dirty Tips
6 Minutes-ish addressing specific aspects of grammar, not genre focused.
Stuff You Should Know
45-60 Minutes of interesting bits of reality. Good for research and idea-sparking.
Youtube Channels:
Write About Dragons
Brandon Sanderson's lectures on creative writing at BYU.
Geek and Sundry--The Storyboard [currently on hiatus]
Patrick Rothfuss hosts discussions about writing.
Extra Credits
This is a show about game development, but many of their topics are equally applicable to creative endeavors of any kind.
Assorted Websites:
Slickwrite
Helps you proofread your own work
Ralan
Pretty much everything you wanted to know about markets
Submission Grinder
A place to keep track of your submission history
David Farland's Daily Kick in the Pants
He kicks you in the pants. You're going to like it.
Forums:
/r/Fantasy
A great place to chat about fantasy
/r/fantasywriters
A great place to chat about writing fantasy
/r/askHistorians
Research abounds
/r/askScience
Even more research
Writers of the Future Forum
Full of dedicated aspiring writers
Codex
Neo-pro writers and beyond. (has qualification requirements, please check to make sure you're eligible before applying)