"Most of the individuals who sustain these injuries lead a sedentary life and only occasionally exercise.  They meet with friends, neighbors or coworkers for a game of soccer, basketball or volleyball, etc..." -- Health & Life--Achilles Tendon Rupture

WebMD Health--Achilles Tendon Problems (great info)

MayoClinic--Achilles Tendon (decent info)

Healthsquare--Achilles Tendon Rupture (basics)

Wheeless' Textbook of Orthopaedics--Achilles Tendon Rupture (very technical)

Lipscomb Clinic Sports Medicine Center--Achilles Tendon Ruptures (gross pictures)

HealthInformatics.com--Achilles Tendon Injury (good description of rehab progression)