I went to law school at UO, so here goes.
Definitely drive at least some of the coast, you can hit the coast directly west from Eugene and drive up to Astoria and then back over to pdx. If you have time check out crater lake (several hours south of Eugene). Also, if you like fishing, it's most definitely worth checking into a fly fishing day trip. There's several great rivers within a few hours of Eugene. Also great wine country around Salem, definitely worth an afternoon of tasting.
In Eugene, definitely eat at pizza research institute and get the apple/walnut/Gouda pizza. If you like beer, go check out the bier stein, plus multiple breweries in Eugene, ninkasi being the biggest. Might be worth a tour. Get a burrito at las morenas, total **** hole on an industrial type road off the beating path, but one of my favorite burritos ever. Sam bond's garage is also a great local bar where you can avoid the college scene. they have local music most nights. They used to have a bingo night that we hit up regularly. And then the campus is really nice to walk around, check out Hayward field (America's most famous track and field stadium) and MacArthur court (pretty sure it's still there even though they opened a new arena). I haven't been back to Eugene since 2007 though so there's probably new stuff to do too.
I also lived in Portland about 8 months before getting a job in DC. Eat at toro bravo. Get donuts (a maple bacon bar) at voodoo donuts. Get breakfast at stepping stone cafe. If you'll be with a wife/gf, walk from burnside up nw 23rd st. Tons of boutique shops and sidewalk cafes/restaurants, very chic area. Also, check out the rosé garden (not the basketball area, the actual garden). If you are there during MLS season and can land reasonable tix to a timbers game, it's worth it for the atmosphere. The best atmosphere in American soccer. Check out Mississippi studios, and the whole Mississippi/Alberta neighborhood in NE. Very cool area. Belmont st and Hawthorne streets in SE are both very cool streets with lots of unique shops. And of course, if you like beer, you can't throw a rock without hitting a brewery in pdx. Depending on when you are going, check on any kind of festivals on the waterfront, during summer, there's some kind of food/beer/music fest almost every weekend. And it's worth wandering around powell's bookstore, the country's largest independent bookstore. It takes up an entire block in downtown. And of course check out the foodtruck scene for lunch at least 1 day. Since I left pdx in early 2008, I've been back a couple times, but don't know all the new stuff, and there's been a huge explosion in new, interesting, highly regarded restaurants, so just use yelp to help guide to more places to eat.
Hope it helps. Sorry if I rambled and got a bit disjointed. I love Oregon though, and Portland is probably the most lovable relatively big city I've ever seen. I'm hoping to move back later this year. Feel free to ask about anything else.