you don't need to cool memory in a system unless you overclock it..... you can get heat spreaders for it, but no reason to.
as far as cooling in general, you can get a PCI slot fan, either an exhaust type fan, or a card like I have w/ two variable speed fans... it's the Vantec Spectrum UV LED fan card. it looks purdy too
just depends what you want it to do.
you could also replace the stock 120mm fan with something quieter and/or something that pushes more cfm of air.