My personal favorite dayhike this time of year is McNeil point from Top Spur trailhead. My Avatar picture was taken from McNeil shelter. In front you can make out Mt. Adams, Mt. Rainier, and Mt. St. Helens. About 100 yards to the left is a 3000ft drop off the side of Mt. Hood. Some of the most spectacular wildflower displays are up in that apline zone, and the huckleberries are ripe by the acre on the route up (as of last weekend).
You should check out www.portlandhikers.com for excellent trip reports. They also have a new field guide with detailed hike descriptions and marked topo maps. I recently posted some photos of my last trip up there at portlandhikers.com.