Improving the "randomness" of a programming function designed for random generation

If using a function like rand() to generate something truly random (insofar the function allows) was the ideal - and the function as it is, falls somewhere on the line between truly random and ordered:

What can be done to improve its random nature? As an academic exercise what could be done to improve its random generation capabilities using some iteration of the function?

Can one create "more randomness" by iteration or combining multiple rand() results in some way?