From the Sierra Club:
What makes this site unique is that it’s a wiki – i.e. anyone can update or edit the trails that are posted. So if I post a trail in, say, Yosemite, and you’ve been there recently and saw that part of the trail is really muddy, or the bugs are bad this time of year, or if camping spots are getting really popular and should be reserved in advance, you can update that.
In addition to various trails, the site also features tips for outdoor adventurers alike, a birding blog, photo contests, and Nature Notes, a series of audio features based on interviews with naturalists and Sierra Club Outings leaders. Sierra Club Trails is also an online community where users can create profiles and meet other bikers, hikers, surfers you name it, as well as join discussion forums with topics like the best trail mix recipe or whether guns should be allowed in national parks. Community members can form groups around a particular outdoor interest or place.
Check it out: trail.sierraclub.org