I could'nt get these methods to work, so I tried something that is pretty much what was suggested above, but without the tpl file. I just created a label called lbl_continue_shop with text reading Click Here to Continue Shopping and added this code to customer/main/cart.tpl below the checkout and submit labels and below the your shopping cart is empty labels:
{$lng.lbl_continue_shop}
This works great for me.