Basic suggestions would be:
External Hard drive wise the cheapest one with e-sata and a decent warranty (Assuming your laptop has e-sata if not it's probly still worth the extra money in case you upgrade to something that does in the future). Search the brand and model before actually buying it to make sure they don't have a tendency to crap out in a relatively short period of time.
Wireless antenna- Don't waste your money unless you are constantly getting less than two bars of reception. Chances are this is only a problem on public (ie. School) or work networks. It's still gonna slower than molasses in winter whether or not you buy one. If your at home a better investment would be a CAT5 patch cable and a few wall face plates to run to your router from your PC.
Note book cooler- I personally like coolermaster products but look at you laptop see where the hotspots are for temperature, typically right below your CPU and GPU find something with fans that will blow air onto or past these spots. Something like
this is pretty decent. If it doesn't have fans to blow air it's just a glorified chunk of plastic/metal and don't even bother with it.