Pawnee Pass and Pawnee Peak is a relatively easy hike close to Boulder with great views of the Front Range. 10 miles roundtrip (4+ to Pawnee Pass, and another 1/2 mile to the peak).
Start at the Long Lake trailhead in the Brainard Lake Recreation area (there's a fee to park, if you don't have a pass). Take the trail towards Lake Isabelle for a few miles, winding through forest and past Long Lake. Signage towards Lake Isabelle and Pawnee Pass is apparent.
Just as you reach Lake Isabelle, look for a junction that heads to the right and uphill to Pawnee Pass. You'll quickly switchback up elevation towards the pass. The views grow just as quickly with the elevation as you climb above treeline and hike across spectacular tundra.
From the trail sign at the top of Pawnee Pass, hang a right to the obvious peak of Pawnee just a short distance and 400ft of elevation above. There is a small social trail if you see it, but you should be able to pick your way up to the peak without any trouble. Scramble across some talus to the rounded top of Pawnee Peak (12,943ft).
If it's clear out, you can see most of the prominent peaks in the region, including Longs, visible to the north. I highly recommend heading up for sunrise!