For detailed trek write-ups and biker reviews, check out this awesome site. TriangleMTB includes both a comprehensive list of the biking trails in the Triangle as well as the openings of said trails (as the status of routes in the triangle routinely close due to regular maintenance, weather, and safety reasons).
While I use this site mainly for hiking, All Trails also includes a well-stocked database of biking trails all across the world. Members of the website are able to upload their own trails, and customer reviews paired with a vetting by the All Trails creators has allowed for a great write up of local trails to be established. Click the button below to check out their website, or search for their app in the app store.
This non-profit both builds trails and tracks trails in the triangle area. Using an interactive map feature, finding your next biking feat is neither difficult nor requires much searching. Reviews from other bikers and write-ups by the authors of the site help guide your search into a trail perfect for your skill set.