A friend from work suggested this book for some good trails around the Front Range, so it has some good bike trails in Boulder and Golden area.  There is also a second book that is suggested by Amazon as a good buy that would complement this one very well.  I have started using the 14er books which are great because they give you a run down of every mountain, directions to each trailhead and difficulty rating of the trail.  I think something for mountain bikes would be awesome so that I can start riding the singletrack trails rather than just the bike paths around my neighborhood.