This year’s classes were held on February 19th, 2011 at Clackamas Community Collage. I suspect ‘next years’ classes (beginning and intermediate) will be held on the closest Saturday to that date and at the same location. They should be posted soon (click on my link below) and fill up fast – so stay tuned 
As mentioned above, I noticed the grafting & pruning events are posted, but there's no registration instructions yet. Any ideas on that info will be available? I've found another class offered elsewhere that's happening sooner, but I'd rather do the one through HOS if I'm certain I can sign up.
Asa
I think that Joanie and Steven posted this to the event part of this site, so I tried to copy and paste it here. Let's see if this works:
HOS Grafting Workshops
Saturday, February 18, 2012, 9am - 2:05pm at the HOS Arboretum
Beginning and Intermediate workshops for hands-on experience with grafting your own fruit trees. Co-sponsored by the Home Orchard Society. Root stock and scion wood provided. Bring your straight edged knife.
9am-10:20am: Beginning
10:45am-12:05pm: Beginning
12:45pm-2:05pm: Intermediate
Co-sponsored by, and registration through Clackamas Community College. Fills quickly, so register soon! $15 each class. Download Registration Form
I guess you'll have to go to the events part of this site to click on the downloadable form.
THanks
John S
PDX OR
Idyllwild
simplepress
jafar
Marsha H
Viron