Some of the best mountian biking trails I've ridden are located here in Bellingham. Having said that I must admit that I have traveled all over the U.S. in search of great trails. Part of the reason I moved to Bellingham was for the great riding.
What makes them so great? Well, to start with you can pretty much start from any location in Bellingham and link up to the innerurban trail system which will take you up to Galbraith mountain or any other trail system in the vicinity. That means no driving to the trailhead for starters!
Galbraith mountain is a vast trail system that has a little bit of everything; From cross country to trials to down hill mountain biking. The cross country riding can be flat will little incline or you can choose a more rigorous route with more hill climbing...really, it's up to you. You can ride for 30 minutes or days on end, without riding the same trail.
For the more daring rider there are man-made stunts and terrain features such as ladders, jumps, and stunts; great for honing in your skills. For the die hard downhill riders there is easy grade fire road for easy access to the top of the trail system so that you don't blow a fuse with your heavy bike. These trails are nicely built with berms, stunts, and jumps. Similar to northshore riding and whistler.
No matter your skill level, don't be intimidated, there are plenty of beginner-intermediate trails to get you on your way. For you cream puff riders there are more than enough great trails/riders to keep you fit. Don't forget your helmet and don't forget to smile!