The following is a terrific resource for dissociation, trauma, PTSD etc:

http://www.trauma-pages.com/

There are some excellent peer-reviewed research articles written by some of the leading researchers in the field that are all viewable free of charge.

There are some excellent articles available from here, too (mostly peer-reviewed)

http://www.johnbriere.com/articles.htm

And I guess I check out this site every now and then as well:

http://www.isst-d.org/