Links, arranged by theme. (More soon.)
Writing Advice:
For undergraduates, Jim Pryor has some excellent advice on writing philosophy essays here. If that isn't enough, there's more advice by Peter Horban here. I personally prefer the Pryor piece, but reading both can't hurt.
For postgraduates, and beyond, I strongly recommend Jonathan Bennett and Samuel Gorovitz, "Improving Academic Writing", in Teaching Philosophy 20:2 (1997) pp. 105-20.
Larry Trask has an excellent guide to writing here. It's extremely informative about various writing conventions, punctuation, etc., but it also provides sensible independent advice about how strictly you should follow those conventions.
Other:
Blogs:
Crooked Timber
Ethics Etc
Leiter Reports
PEA Soup
Philosophy, Et cetera
General Resources:
Philpapers
Stanford Encyclopedia of Philosophy
The Philosophical Gourmet Report