The Actor's Library at The Book Store has many excellent books on acting. These include Audition, How to Audition, etc.
Go to:
The Book Store
http://thebookstore.vstoremarket.com/index.htm
Put "actor" or "audition" in search engine. If you're looking for a specific book on acting, then you can put that in the search engine also. The Book Store also has a lot of books on Digital Filmmaking.
Anyone interested in writing web content for actors, including information on online resources for actors:
http://www.constant-content.com/?aref=2957
You can also publish content on acting and/or other subjects at:
http://www.associatedcontent.com
Both of these markets are paying markets. For Associated Content, you need a paypal account. Sign up for paypal via this link:
http://www.paypal.com/us/mrb/pal=P6ZD9EV3H7GL4
You can also find information on acting jobs & jobs in the entertainment industry at:
http://www.showbizltd.com/index.cfm?affiliateID=3765