phonography.org is one home base for this field (pun intended). The best resource here is the personnel list, since the gear page is out of date and spare.
Better for the equipment side of things is the Vermont Folklife Center, which has a thorough Audio Field Recording Equipment Guide.
The BBC have some basic courses online, though these focus on radio.
I feel I must point out this insane recorder, especially for those planning their next Antarctic field trip.
The Freesound Project is an audio clip resource. Recently a nice article, The Adventures of a Freesound Member, was posted.
One of the most famous sites for phonography, and rightly so, is The Quiet American. Every week a new One Minute Vacation is added. These are unedited excerpts of sound from somewhere and somewhen. Fascinating.