Blender - Rendering from the command line

Render an Image:
blender -b [directory of file] -o [output] -f [frame number]

Render a Video:
 blender -b [directory of file] -o [output] -s [start frame] -e [end frame] -a

http://wiki.blender.org/index.php/Doc:2.6/Manual/Render/Command_Line