Events

Double-Rugged Ride and Tie
A 20K trail bike and run team relay event. Teams of two trade a mountain bike for some trail-running and vice versa (for around 10 km of each) near the Boulder Reservoir, Colorado. Held annually in October.
http://www.5430sports.com/

The MORPH
The race is entirely off-road and consists of a triathlon (run, kayak, bike) or biathlon (run, bike). Both events are for ages 16 and over. Features dates, history, overview, photo gallery and links.
http://www.the-morph.co.uk/

Oddman 1.3.5
Part of the New Jersey Biathlon series, a 3-race series which includes two King of the Hill Off-Road Biathlons. This annual 5 km trail run, 10 km mountain bike race features registration information, results archive, photo gallery, and links.
http://www.oddman135.com/