Reuters reports on a study that demonstrates exercise builds new brain cells, something of particular interest to 30-something geeks like me since:

Tests on mice showed they grew new brain cells in a brain region called the dentate gyrus, a part of the hippocampus that is known to be affected in the age-related memory decline that begins around age 30 for most humans.

My memory is bad enough as is -- I can't afford to lose any more. Good thing I've been hitting the gym so enthusiastically for the last year.