Useful websites for students interested in participating in collegiate athletics:

NCAA Eligibility Center
Visit this site to complete the NCAA Initial-Eligibility form, a requirement for student athletes interested in playing Division I or II sports. 
http://web1.ncaa.org/ECWR2/NCAA_EMS/NCAA_EMS.html#

NCAA Eligibility Center Quick Reference Guide
Visit this site for a quick reference guide to NCAA eligibility requirements (GPA, Test Scores, etc).
http://fs.ncaa.org/Docs/eligibility_center/Quick_Reference_Sheet.pdf

NCAA Eligibility and Recruiting Guidelines
This site is most helpful for students interested in eligibility requirements and recruiting calendars for individual sports.
http://www.ncaa.org/student-athletes/resources/division-i-initial-eligibility-toolkit

National Collegiate Athletic Association
Official Web site of the NCAA
www.ncaa.org

National Association of Intercollegiate Athletics
Official Web site of the NAIA
naia.org

University Sports
An organization that specializes in helping top student athletes contact college coaches.
www.universitysports.com