Automatically move files when inserting SD card?
From this question on SuperUser, try MarcoPolo

Or, you could use folder actions.

From this tutorial:


  
  Go to File > Save As Plug-in.
  Choose Folder Action from the pop-up menu.
  In the Attach to Folder pop-up, select Other…
  In the resultant open dialog, hit cmnd-shift-g. This will bring up a small sheet labeled Go to the folder:.
  In this sheet, type /Volumes/, and hit the Go button, then hit Open.
  Hit the Save button in the Plug-in sheet.