Trillium Lake, near the campground of the same name, is a very popular cross-country skiing loop. White River Canyon is another good trail, and starts at a Sno-Park on Hwy 35 (about 4 miles north of Hwy 26).
Mt Hood Meadows offers around 10 miles of groomed wooded trails. Several other free (ungroomed) trails start from the same parking area, including an easy 1.3-mile trail to Sahalie Falls and another, more challenging one to Elk Meadows.
An outstanding guide that includes Mt Hood hikes is William L Sullivan's 100 Hikes in Northwest Oregon. It's also worth visiting a ranger station for maps and current information on the many hikes in the area. A Northwest Forest Pass (per day $5) is required at most trailheads.
A popular trail loops for 7 miles via lovely Ramona Falls, which tumbles 120ft down a face of mossy columnar basalt. To reach the trailhead from Zigzag, turn north onto Lolo Pass Rd, continue for 4 miles, then turn right onto USFS Rd 1825 and drive 3 miles further.
Hike a mile up from Hwy 26 to Mirror Lake, which reflects Mt Hood beautifully. You can hike a half-mile around the lake, then 2 miles beyond the lake to a ridge top. The trail begins between Miles 51 and 52 on Hwy 26, about 1.5 miles west of Government Camp.
Walk 2 miles (one way) on the gentle Old Salmon River Trail through riverside old-growth forest along the Salmon River. To reach the trailhead, turn south from Zigzag on Salmon River Rd and drive 2.6 miles. The trail follows the road, but the walk is still outstanding.
The mother of all trails is the (approximately) 40-mile Timberline Trail, which circumnavigates Mt Hood along a scenic wilderness of waterfalls, quiet reflecting lakes, wildflower meadows and mountain vistas. Parts of the trail may be closed due to washouts or fallen trees (one section was rerouted after a flood in 2006), so check with ranger stations as you plan your hike, especially in spring. The trail can be accessed from several points – noteworthy sections include the hike to McNeil Point and the short climb to Bald Mountain, both offering breathtaking scenery. From Timberline Lodge, Zigzag Canyon Overlook is a 4.5-mile round-trip through meadows of wildflowers to a canyon vista. Some trails can be snowbound until late July, and fording rivers can be a challenge, so stop in at a ranger station for details before you decide on which part of the trail to take on.
Climbing Mt Hood
Mt Hood (11,240ft) is the second-most-climbed peak over 10,000ft in the world, after Japan's Mt Fuji. This isn't to say Mt Hood does not require both climbing skills and stamina; nearly every year, a few people die making the ascent. Climbing is best between May and mid-July, and a typical climb from Timberline Lodge (where registration is mandatory) takes eight to 10 hours round-trip for a fit person. If you're not an experienced climber, be safe and go with a guide service, such as the Northwest School of Survival or Timberline Mountain Guides.
Portland's Mazamas is a mountaineering and hiking club (not a guide service) that educates people interested in mountaineering and sponsors climbs of many Northwest peaks, including Mt Hood.
When the snow is gone, Mt Hood SkiBowl is transformed into a mountain-bike downhill arena; bike rentals are available. If you're more the cross-country type, however, cross Hwy 26 to the free Government Camp recreational-trail network. The Crosstown Trail is a fairly easy 3-mile single track between Glacier View and the Summit Ski Area. More challenging trails sprout from it.
Most of the cross-country skiing trails in the area are good for summertime mountain biking.
Permits & Passes
If you park at certain designated winter recreational areas from November 1 to April 30 (ie for cross-country skiing or snowshoeing), you'll need a Sno-Park permit (one/three days $4/9, annual $25). These are available at Government Camp gas stations, DMV offices, most outdoor retailer shops and Timberline Lodge.
During the rest of the year, a Northwest Forest Pass (daily $5, annual $30) is required to park at most hiking trailheads; buy them at ranger stations and outdoor retailers.