This commonly abused verb is derived from the French compris, the past participle of comprendre, meaning to comprehend or contain. Thus, to comprise is to include, sum up, or consist of. Note that the whole comprises the parts; it is not comprised of them. The frequency with which this blunder is observed is undoubtedly due to widespread confusion between comprised and composed. The following, for example, is taken from a CNN article:

The six comprised a terrorist cell, the government said, that was "directly related," with two people detained recently—Tunisian Nizar Trabelsi, who was arrested earlier this month in Belgium, and Jermoe Courtellier, alias "Selkman," who was arrested in Holland.
Perhaps less surprising is the appearance of the following definition in Webster's 3rd, a dictionary noted for promoting just this sort of abuse:
²disjunct: Any of the alternatives comprising a logical disjunction.
The OED also recognizes this usage, but characterizes it as "rare", citing two instances, both from 1794. This is consistent with the following usage note provided by
Since the late 19th century it has also been used in passive constructions with a sense synonymous with that of one of its original meanings “to consist of, be composed of ”: The United States of America is comprised of 50 states.
In fact, I have dicovered that the error dates back much further, to a 1661 translation of Euclid's Data:
Seeing then the angles comprised of equal right lines are equal, we have found the angle FDE equal to the angle ABC; ...
See my Language Log post for details.