When did the universe start expanding? Will the universe expand forever? Here are some resources that consider the field of cosmology:

Cosmos in a Computer
This vast "multi-media exhibit" created by the National Center for Supercomputing Applications in Illinois is really a tutorial in cosmology - the study of the BIGGEST questions in astronomy. How did the universe begin? What does it look like on the largest scales? Will the universe end? This site contains QuickTime movies, sound files, and lots of graphics, so a fast connection helps.

Dr Odenwald's essays on Cosmology and Big Bang Theory
Interested in some of the mind-stretching implications of the Big Bang Theory? Dr. Sten Odenwald, an astrophysicist working at the Goddard Space Flight Center in Maryland, has created this web site that contains some articles he has written for the magazines "Sky and Telescope" and "Astronomy." The site also contains links to answers to frequently-asked questions about the Big Bang. Warning: Dr. Odenwald's "semi-popular" style of writing can be rough-going for the newcomer to cosmology.

To help you envision an expanding universe try this activity.