I will be at the Marriott in Clackamas, and will be driving the I-205 to get to Reed College at 8:00am. What is the traffic like? Do I need to allow extra time?

Well, yes, it's rush hour, I'd definitely allow extra time, at least Mon-Fri. You'll probably be taking Highway 224 west from Clackamas to Highway 99e (McLoughlin) going north, to Woodstock. I've not driven those roads at rush hour but I'm fairly sure you can expect some decent traffic. If you need to be there at 8, better to be a few minutes early.

I don't think I would take 224 to get to Reed due to traffic on 224.

You might be better off heading north on 205 and taking the Foster Rd exit, which will loop you around and then you will need to head west on Woodstock and it will bring you right to the college. Maybe someone who lives on or near Woodstock can tell you if traffic on Woodstock is bad during rush hour?

seremarcus;
can't offer any advice, but noticed you are going to Reed College.
Great school, my daughter graduated '93. And taught there as an adjunct professor around 2005.

Andrew, you can't easily get to Woodstock from McLoughlin (Hwy 99E) northbound.

Eurotraveller's got the best route. Foster Rd. exit off of I-205, south a few blocks to Woodstock (I'd suggest going down to 82nd and then south a few blocks), and from there it's a straight shot down to Reed.

Traffic shouldn't be too bad.