#!/bin/sh 
find /mnt/tank0/.recycle/* -atime +14 -exec rm -rf '{}' \; 
find /mnt/tank0/.recycle/ -depth -type d -empty -exec rmdir {} \;

Update 2011/03/04: Updated the script to delete empty directories by adding:

 find /mnt/DATA/.recycle/ -depth -type d -empty -exec rmdir {} \; 

which was suggested by Alan in the comments below. Thanks Alan for the updated script!