Now available: There's a great updated edition of John Zilly's guidebook to mountain biking Northwest & Central Oregon. Zilly's an entertaining writer and obsesses over all the relevant details to give accurate descriptions and information. This update adds many rides not found in the first edition, including the North Umpqua Trail. The maps are excellent. If you are looking to add some new rides to your summer, this is a great resource for planning and daydreaming. You can get it at many local bike shops or:

http://www.powells.com/biblio/2-9781881583127-0
or
http://www.amazon.com/gp/offer-listing/1881583120/ref=dp_olp_2?ie=UTF8&qid=1215029813&sr=1-2

Also check out:
http://www.adventurepress.com/books/books.htm