Mt. St. Helens

Lava Canyon is an amazing day hike. Fantastic scenery and a great, bouncy suspension bridge to boot! I would highly recommend it. Ape Cave is only a mile or two away and both can be done in a day. Windy Ridge is also nearby and there is a short trail at the Independence Pass Trailhead that can be done as a five or six mile loop with view to the crater, Spirit Lake, and the Mt Margaret Ridge. I recently did a three-day trip in the Mt Margaret Backcountry north of Spirit Lake. The description is posted on this website (Lakes Trail #211). The trail along Coldwater Lake is beautiful, especially when the wildflowers are in bloom in late June/early July. You could hike to the end of Coldwater Lake and return the way you came for an eight mile round trip (or less). There are an incredible variety of landscapes, meadow, forests, waterfalls, etc. in just this portion of the trail. The scenery is unlike anything else because it is all in the blast-zone of the 1980 eruption.

Lava Canyon is supposed to be pretty impressive.

There is a short little hike to June Lake on the south side of the mountain. I think its only two or three miles, but the lake is quite impressive, with a lava flow on one side, and a large waterfall plunging into it on the other.