This article is from the Fitness FAQ, by Jeff Gleixner (firstname.lastname@example.org) with numerous contributions by others.
First, locations of basic muscle groups from the feet up to the hands:
Calves: Back of leg, between the knee and ankle. The two main
muscles in this area are the Soleus, lower area, and the
Gastrocnemius, the "meat" of the calves.
Quadriceps (Quads): Front leg between the waist and knee. (Thigh)
Hamstrings (Hams): Back leg between the butt and the knee.
Gluteus Maximus: Butt.
Abdominals: Front of body between chest and groin. Also consist
of the Obliques, which are on the middle and outer walls
of the abdomen.
Latissimus Dorsi (Lats): Between the Spine and the sides of the
ribs starting near the from the armpit and going down to
the last rib. Gives people the "V-Shape", along with a
Trapezius (Traps), Between the back of the neck and the shoulders
tapering to the middle back area.
Pectorals (Pecs): Chest.
Deltoids (Shoulders): Made up of 3 muscles.
Middle: Medial Deltoid
Back: Posterior Deltoid
Triceps (Tris): Back of the upper arm, making up about 2/3 of the
Biceps (Bis): Front of the upper arm, accounting for the other 1/3
of the upper arm.
Forearms: Between the elbow and wrist.