I have been using zopnow.com for the last couple of months and I have to say that all my expectations were blown away by their delivery timings. I got same day delivery when I put in the order as late as 11:30 AM and always got next day delivery while ordering late in the night. Their customer service is also awesome (one product was out of stock and they replenished it within 3 days)
The only downside (if I looking for it) is that the prices are average. You might miss some of the specials that the local retail outfits run periodically, but the fuel price savings and their loyalty program more than makes up for it.