In the same way that your money is not immediately refunded it will just take a little time and after a while they should no longer appear. If they have been sitting there for some time now (days) then I'm not sure as I've never had that happen.
EDIT: Ah! I just remembered. If you uninstall the app from Settings it doesn't refund your money. Make it your practice that when you download a paid app, to uninstall it from the Market so they you get the option to Uninstall & Refund instead of just uninstalling.