For the visual, Yahoo! provides a public-domain version of Gray's Anatomy which not only provides images of the femur and its features, but also explains them in much more detail than me. http://education.yahoo.com/reference/gray/subjects/subject?id=59#p
The femur is the longest bone in the body, and makes up one quarter of an individual's height. Because it is the strongest and heaviest bone, it survives environmental extremes and is often found at archaeological sites. Unknown specimens are useful in estimation of stature.
The femur articulates proximally with the innominate, or hip bone, at the acetabulum--the socket part of this ball and socket joint. Distally the femur connects with the tibia and patella. It does not articulate with the fibula.
The hip joint allows for circumduction and axial roation; the joint is a multiaxial ball and socket joint. It is the second-most mobile joint in the body, after the shoulder joint.
The femur ossifies from five centres: the shaft, head, and distal end, and one for each trochanter.
The four major features of the proximal end are the head, neck, greater trochanter, and lesser trochanter:
The femur's head forms two-thirds of a sphere, and is directed medially, upward, and forward. The depth of the acetabulum, or hip socket, means that the head is very secure in its socket; this security comes at the expense of a decreased range of movement, compared to the similar shoulder joint. The depression near the centre of the head is the fovea capitis; the ligamentum teres from the acetabular notch inserts into it. The position of the fovea capitis is useful in siding isolated femoral heads, as it is displaced inferiorly and posteriorly from the centre of the head.
The neck of the femur is shaped like a truncated pyramid, with the head at the narrow end and the greater trochanter at the wider base. The neck attaches to the shaft at an oblique angle. Features on it include the intertrochanteric line, to which the iliofemoral ligament (the largest ligament in the body) attaches, giving extra strength to the hip joint. The posterior aspect of the neck is separated from the femoral shaft by the intertrochanteric crest, a rounded ridge between the greater and lesser trochanters.
The lesser trochanter is a traction epiphysis, or an ossification center arising near a site of tendon attachment. The tendon in this case is the iliopsoas, which flexes the hip. The lesser trochanter has a conical shape.
The greater trochanter is also a traction epiphysis, for Glueteus Medius, which moves the femur upward, medially, and backward. Gluteus Minimus inserts anteriorly, and Medius posteriorly on the trochanter. The greater trochanter is also the location of the quadrate tubercle, the site of insertion of Quadratus Femoris. Obturator Externus inserts at the trochanteric fossa on the medial side. A groove for the tendon of Obturator Externus extends across the posterior neck from the trochanteric fossa; this groove is useful in paleoanthropology, since it would only be present on the bone of a biped.
The proximal end of the femur also has several minor features.
The gluteal line or tuberosity extends from the base of the greater trochanter to the lateral lip of the linea aspera. This line can be either a depression or a tuberosity. It is the site of insertion for part of Gluteus Maximus, the muscle which extends and laterally rotates the thigh.
The spiral line is inferior to the lesser trochanter. It joins the inferior end of the intertrochanteric line to the medial lip of the linea aspera, and is the origin for part of the knee extensor, Vastus Medialis. The spiral line's simple name is easy to explain; the intertrochanteric line and the linea aspera are nearly on opposite sides of the femur, and in connecting these two features, the spiral line is curves around and down the bone.
The pectineal line, slightly curved, extends from the base of the lesser trochanter to the proximal end of the linea aspera, between the spiral line and gluteal line/tuberosity. It is the site of insertion for the muscle which laterally rotates and flexes the thigh--Pectineus.
The linea aspera is a rough, elevated ridge on the posterior femoral shaft. The spiral, pectineal, and gluteal lines merge into the linea aspera at its proximal end; at the narrower distal end, it divides into the medial and lateral supracondylar lines. (If you were to do a line drawing of the linea aspera, with its three lines at the top and two at the bottom it would look like a rejoicing stick person.) The linea aspera is the main site of origin for Vasti, and the primary insertion for several Adductor muscles. In the bone of a muscular individual, this feature can be extremely pronounced. Even in a non-muscular individual, it is prominent enough to be easy to find.
There is a nutrient foramen in the posterior midshaft region of the femur, either on or adjacent to the linea aspera. Bones need to eat too.
The popiteal surface is a triangular flattened area on the posterior distal femur--basically the space between the supracondylar lines and the condyles.
The most prominent features of the distal femur are naturally the medial and lateral condyles, but there isn't too much to say about them. In life, they are covered in hyaline cartilage, and they form part of the knee joint. The medial condyle extends somewhat more distally than laterally.
Between the condyles is the intercondylar fossa, a non-articular U-shape. Within the fossa are two facets, to which attach the anterior and posterior cruciate ligaments.
At the outer aspect of each condylye is an epicondyle, one each for the medial and lateral collateral ligaments. The proximal surface of the lateral epicondyle has a facet for part of Gastrocnemius, which is involved in the motion of both the knee and ankle. On the posterior surface of the lateral condyle is a groove for the Popliteus tendon, known as the Popiteal groove. This fairly visible feature can be described as a hollow channel.
On the anterior distal portion of the femur, the cartilage covering the condyles extends forward to create an anterior articular or patellar surface or trochlea. The lateral lip of this surface projects further anteriorly and superiorly than the medial lip, which is useful if you need to side fragments. Unsurprisingly, the patella articulates with the patellar surface.
On the medial supracondylar ridge, just superior to the medial epicondyle, is the Adductor tubercle, site of insertion of Adductor Magnus. The lower femoral epiphyseal line runs through this tubercle and along the intercondylar line.
Some femurs may exhibit platymeria, a marked anteroposterior flattening of the upper part of the shaft. Presence or absence of this characteristic may be indicative of biological group or affinity.
Sources
Really entirely from Dr. Donaldson's lectures in Anthropology 451: Human Osteology at the University of Victoria
Some reference made to Wikipedia, but not very much, really, because their article on the femur is broken up into not-very-user-friendly sections.