When I lived in Seattle, I had good luck with Stupice, Early Swedish IPB, Peron (Sprayless) and all the cherries. And by putting a beach umbrella/tent over the plants to try and control the late blight by keeping them dry.

Carla in Sac

I grew Anna Russian last year, and this variety did very well considering how awful the growing season was last summer. It tastes great, and is very versatile. Also it has wispy foliage, and I think this helps with ventilation issues which can cause disease. That's a big advantage around here with our damp climate IMO.

The absolutely most fool-proof tomato I have ever grown is Siletz, which doesn't even need to self-pollinate to set fruit, so it can handle cool and damp climates just fine. Some people say Siletz is not very flavorable, others think it is just fine. At the very least it is as good as other very early tomatoes, and much better than supermarket tomatoes. I would say it's a good early tomato... it produces a lot of decent-sized beefsteak fruit and is determinate, so it merely needs staking.

There are several cool season toms that were developed at the Oregon State University, Siletz and Oregon Spring being two. You might check Hume Seeds, local to the PNW to see what toms they have listed.
As mentioned, Stupice was very popular in WWA where I'm from. I would think most of the short/cool season toms would grow well there, especially the Russians. Tomato Growers Supply lists their toms by season, so you can see quickly which ones might work for your area. Also Tatiana's Tomato Base has a lot of catgories/info and she's based in the PNW(BC). HTH

Tatiana's tomato base is a good resource. There are tons of varieties in the wiki on this site, and hundreds of them are grown by Tatiana each year. She also sells seeds, which are very reliable!

tatianastomatobase.com

For any variety, the growing notes listed under B.C K O T are by Tatiana, who lives near Vancouver, BC. I am pretty sure that anything that has grown well for her in Vancouver has a decent chance in Seattle if you take good care of it.

I'd like to add a follow-up question:
When can I plant tomato plants this year here in Renton? A friend gave me a few plants yesterday and I don't know if it's too early or not. Any suggestions are welcome.

Most people wait until mid may or later for Seattle. Last frost date is April 20, and you can plant them earlier if you build a hoop house, but otherwise you should wait until nighttime temperatures are consistently around 50*F or higher. I think this is usually May 15 or later, at least in North Seattle.

Thanks for the quick response, plantslayer, I appreciate it. I guess I'll keep the plants I have now in the house until then.
I can't wait to get going out there - this winter and spring have been so dreary - I need to get out there and put my hands in the soil :)

stupice is the one.
Not very large, taste quite a bit better than store bought but not stellar.
I plant a few every year as my Plan B.
Last year they were the only ones that produced more than 1 ripe tomato out of ~60 plants. Dozens upon dozens each.

Siletz, Legend, and oregon spring are close seconds.
Taste... uhh, better than store bought.
My mom loves them. Me, not so much.

/me reaches for his tomato porn

Carolyn recommends Matina and Sophie's Choice.
SC is better tasting than stupice and much larger, but still
with all the early greatness.
I have grown Sophie's Choice once and it was quite a performer for such a small plant. Slugs got most of em, but what they missed tasted great.
I'd grow it again if I hadn't lost the seeds.

We grew Matina last year, and it was very early, but for us it was small, kind of sour, full of jell and had a thick skin. I can't really recommend that one... then again, I got my seeds from trade so maybe it wasn't the true variety. I really do want to try Sophie's Choice some day, a lot of people have recommended it.

I recently read about 2 varieties with great taste in our area in The Resilient Gardener. The author recommends Stupice and Amish Paste, so I plan to try those for 2012 tomatoes.