The Vector Field Analyzer, written by Matthias Kawski at Arizona State University, is a very nice JAVA program for visualizing vector fields. It will run automatically if you go to the above website; you can also try the "official" website. Unfortunately, no documentation for this program currently exists; the software is still being tested. However, minimal instructions do exist for an earlier version of the program, which you can find here.
Some further information from a similar course taught elsewhere can be found here.
For additional information, please contact Tevian Dray at tevian@math.oregonstate.edu