What is a normal range for testosterone levels in a man?

Depends on the lab. The exact normal range of testosterone in men will depend on the lab performing the test. In general, it is approximately 250-850. One should also be aware of the free testosterone level, which is more accurate test to determine if one is making (or using) enough testosterone.
About 450 - 900ng/dL. Here is the source for that quote: http://www.Androgelpro.Com/common/images/chart_normalhealthy.Gif the values above represent a morning blood draw {optimal time = 8am} of a total testosterone level.