jhead -n DSCN0382.JPG
DSCN0382.JPG --> 0408-150734.jpg
any strftime argument can be given as well:
jhead -n%Y%m%d-%H%M%S *.jpg
This will rename files matched by *.jpg in the format YYYYMMDD-HHMMSS
jhead -n%Y%m%d-%H%M%S DSCN0382.JPG
DSCN0382.JPG --> 20120408-150734.jpg
see also the man page for lots of other cool options. You can for instance correct (shift) the EXIF date. This is very handy when merging files from different camera’s when some camera’s have an incorrect time set.