The ultra-popular Brainard Lake Recreation Area is, more properly, actually two trailheads. However, they are accessed by the same roads and suffer from identical red tape.
Brainard Lake itself is a small lake at the junction of two major valleys in the east central Indian Peaks Wilderness. The northern of the two valleys holds Mitchell and Blue Lakes, while the southern valley holds Long Lake and Lake Isabelle. The standard routes on at least eight popular peaks named peaks start at one trailhead or the other the area is justifiably popular.
The Brainard Lake road starts at the town of Ward on the Peak to Peak highway (CO119). From Nederland, drive north for 8 miles. You can also access Ward directly from the Plains via Lefthand Canyon (CO 16) between Boulder and Lyons.
From the intersection with the Peak to Peak, head west on good road (paved) as it switchbacks through beautiful aspen forests. At 2.5 miles, encounter the fee station and gate.
When the gate is open (typically June 1 through early October, dates vary tremendously and seemingly at random), a caretaker will relieve you of $8 for a five-day pass. A season pass is also available. Drive another 2.5 miles to Brainard Lake. A one-way road loops around the lake. At the half-way point on the loop, a marked road leads to the Mitchell (right) and Long Lake (left) trailheads. Both trailheads are quite large, but incredibly popular. You may find yourself parking back down at Brainard Lake (parking spots are available on the left hand side of the road) and hiking the last half mile. Note that for the Long Lake trail, the Niwot Cutoff will save you some distance.
When the gate is closed (mid-October through Memorial Day, dates vary tremendously and seemingly at random), you can access Brainard Lake for free, but you'll have to walk to get there. There is a small parking area at the winter closure gate (technically known as the Red Rocks Lake Trailhead) with room for perhaps a dozen cars. Several popular snowshoing and XC ski trails depart from here or you can hike the road (relatively pleasant as these things go). This trailhead also provides access for Niwot Mountain and the Sourdough Trail.
Another option in fall or spring is to bring a bike and bike the last 2.5 miles to the trails themselves. Bikes are not allowed on the trails, but the paved road makes easy going and will cut five miles off your off-season round trip.