Also a good site know about, if you are the adventurous type is http://recwell.umd.edu/Adventure-Program
They offer great hiking, camping, kayaking, paddle boarding. canoe, whitewater, cabin, etc trips. You just have to keep your eye out for the adventure trip signups because they are small groups and book up VERY fast.
Also check out these classes for something different - some are offered only in fall, some only in spring http://innovation.umd.edu/learn/fearless-ideas-courses/