Archery
Badminton
Basketball
Beach Volleyball
Boxing
Canoe/Kayak (Flatwater and Slalom)
Cycling* (Track, Road, Mountain Bike and BMX)
Diving
Equestrian
Fencing*
Field Hockey
Gymnastics* (Artistic, Trampoline and Rhythmic)
Handball
Judo
Modern Pentathlon
Rowing
Sailing
Shooting
Soccer (aka Football)
Swimming*
Synchronized Swimming
Table Tennis
Taekwando
Tennis
Track & Field* (aka Althetics)
Triathlon
Volleyball
Water Polo
Weightlifting
Wrestling
*Contested at every summer Olympic games since 1896
Added for 2016:
Rugby Sevens
Golf
Discontinued Olympic Sports:
Baseball -- Dropped after 2008 Olympics
Cricket
Croquet
Jeu de Paume
Lacrosse
Motor boating
Obstacle Race for Swimming
Plunge for Distance
Polo
Racquets
Softball -- Dropped after 2008 Olympics
Tug-of-war
Underwater Swimming