I attended the 2009 Colorado Summer Seminar in Philosophy. It's really a great opportunity to see another philosophy department, meet some very motivated and intelligent peers, and learn from some amazing professors. The costs posted above do not include travel and most meals. From what I remember, Colorado does not offer any scholarships. This is so they can keep the costs of the seminar as low as possible for everyone. However, as the previous poster suggested, you can ask your department if they have scholarships for students to attend seminars or conferences. Also, the topic need not be one's potential area of study.
Carnegie Mellon also has a Summer School in Logic and Formal Epistemology. This includes tuition and housing, but the students are responsible for travel and living costs. However, this program does not offer students a grade, so it might not help as much as the Colorado seminar in the long run. That is, unless you are interested in logic or formal epistemology. A link to more information: http://www.phil.cmu.edu/summerschool/