for Search Engine optimization, one small thing you can do to get things entered in the engine is to turn on SE friendly URL's. Go to your site and click on an item.. you see that URL at the top that looks like
Shopcorrect.com :: Computers :: Laptops ? Search engines don't like that. It's dynamic content, so they don't want to index it as much because it seems pointless. A search engine friendly URL would look more like
http://www.shopcorrect.com/store/com...e/iphones.html
Search engines like these URLs much better and it will take you 5 seconds to do it while you're managing your other store stuff.
Many shopping carts are compatible with forums such as vBulletin and SMF, so for reviews you should either install one of those or some other kind of commenting system. Forums now usually include the capability to add a blog so that wouldn't hurt either.
If you want some good marketing, set your paid ads aside for ten minutes. These forums are a great idea, spend 10 minutes every day going to different forums and posting, but don't post just to advertise. I hate that, and so do most other people I know. Post something relevant that is helpful to someone somewhere and on topic.
Also, as I seem to keep telling everyone... offline marketing. If you're paying $50.00 for enough online ads to acquire one sale on your site, spend the same $50.00 in offline marketing and use your noggin about placement. Newspapers are HORRIBLE. I've never had a bit of luck with them. What I have had luck with are posters and fliers. They're cheap and efficient. if you can get 50 posters for 50 bucks, make sure you can get a deal on your website that people won't find anywhere else. Print up the posters and put them up all over the place. Perhaps put a coupon code on them so you'll know when people use them.
I should mention in offline marketing that you should deal with a metrics software that can help you keep track of your offline stuff as well as online for things like Cost Per Acquisition, ROI and the other regular stuff.