What is the difference between colds & flu?

So, other than being caused by different viruses, what are the differences between having a cold and having the flu? How can one tell by one's symptoms?

 Colds and flu can present with similar symptoms, but flu is distinguished by body aches and fever. A cold can produce a low-grade fever (under 100*F) but flu will produce the real thing (over 100*F). Both are contagious for about the same amount of time, with variance depending on the particular virus.

From the CDC website:

The period when an infected person is contagious depends on the age and health of the person. Studies show that most healthy adults may be able to infect others from 1 day prior to becoming sick and for 5 days after they first develop symptoms. Some young children with weakened immune systems may be contagious for longer than a week.

And according to Dr. Sears, the famous pediatrician:

In general, a cold is contagious from about 24 hours before onset of symptoms until about 5 days after onset.