Go to the Widmer Brewery. It's been around for over 15 years and is the brewery that introduced seasonal beers to the United States. It is most famous for Hefeweizen, but has a good slate of offerings for any taste bud. The menu for food here is pretty good, too. The brewery offers tours and sells all sorts of beer-related items.
Stop in at BridgePort, Oregon's oldest craft brewery. There are two pub locations in Portland, one in Northwest and one in Southeast, to cover you no matter what side of the Willamette you find yourself on. Its IPA recently won the world-championship trophy, and it will be served to you in "Imperial" pints - that's 20 ounces. Take a free tour if you want to see how it all comes together.
Take your pick from one of the many McMenamins locations sprinkled all over town and the outlying areas. This is an institution in Portland. Buildings run the gamut from a renovated hotel to old, restored movie theaters where you can grab a beer and a slice of pizza and watch a movie. McMenamins beers offer a full range of microbrews, with some great seasonals like Purple Haze.
Check out the renovated warehouse known as the Lucky Lab. It's a smoke-free, laid-back pub in the heart of Southeast Portland. Most menu items come in under five bucks, and on Mondays, 20-ounce pints are just over two bucks. The Lab's beers here cover a broad range of tastes from pale ales to porters.
Head over to Portland Brewing, home of McTarnahan's Amber Ale. Every year Portland Brewing has a charity keg-tossing contest, and the throwers have to wear kilts. The Taproom in Northwest Portland serves up great pints and food to go with them. Portland Brewing offers a tasty core of staple beers and throws some great seasonal mixes in to keep it interesting.
Graze the selection at Belmont Station if you can't decide on a brewery or a beer. This is a terrific store that offers most local labels and flavors in bottle for sale. Oh, and for those coming to Portland from far away, Belmont Station will deliver as much as you'd like wherever you'd like it to go.