I'm definitely a fan of the "resealable bag" innovation on groceries.  It's nice to have that extra peace of mind in knowing that the food I just opened won't spoil or dry out overnight.  But what about the select bagged foods that don't have those convenient zip-tops?  Well, you could try this...

This should provide a better seal than only using a clothes pin.  Just be careful not to cut yourself while you make this one!