Views of the Solar System: Oort Cloud
Definition and overview.
http://www.solarviews.com/eng/oort.htm

What's in the Oort Cloud? Both Less and More, New Study Suggests
Article discusses the nature of the spherical cloud of comets that surrounds our solar system.
http://www.planetary.org/html/news/articlearchive/headlines/2001/Oort1.htm/

Electronic Universe: Oort Cloud
Discusses the proposed vast cloud at the outer reaches of the solar system.
http://zebu.uoregon.edu/~js/glossary/oort_cloud.html