Besides two rather expensive B&Bs, there is no lodging within walking distance to campus (unless you like hiking). Econo-Lodge and Super 8 are on Willamette river next to highway 34 about 1.5-2 miles from Bexell Hall, where the talks will be held. Both look nice from the outside.
Jason Inn on the 9th Street is a standard motel, clean but somewhat worn-out. It's also about 2 miles from Bexell. Motel Orleans, Ramada, Salbasgeon Suites and Shanico are further up on the 9th Street perhaps 3 miles from Bexell. These are definitely nicer than Jason Inn but also more expensive. OSU often uses Salbasgeon to accommodate its more important visitors (i.e., generous contributors).
Finally, Towne House Motor Inn is in the southern part of downtown Corvallis on a busy thoroughfare about 2 miles from Bexell. Of course, this is Corvallis, so the traffic will be nothing like you've used to seeing in Seattle. The Inn is a standard motel, but it looks fine from the outside.
Parking on campus is free on Saturdays and Sundays. There is a parking lot just north of Bexell next to Weniger Hall. It this one fills up, there is a large parking lot on the other side of Weniger.