A service that would, once a month, deliver by mail ALL of your needed toiletries - toothpaste, shampoo, shaving cream, deodorant, soap, etc. These would be the products you use normally - Old Spice, Colgate, Gillette, etc. The prices would be equal to, or often less than the store prices.
I don't know how profitable it is for Amazon (since the items are 15% off and they ship free), but it has worked out well for my fiancee and me. For things that we would have bought at Costco (shampoo, toothpaste, lotion), we are saving a little and we don't have to make that extra trip to Costco or carry heavy items from the car.
If I heard this startup pitch I would want to know what experience you have in retailing and especially logistics. I wouldn't care at all about your web or programming expertise.
Suppose you were doing this without computers or the web. Customers filled out a paper order form and you then fulfilled their standing orders. This is very similar to what Schwann's and diaper services do now, and what milk trucks did when I was a kid. 75% of the problems you need to solve will be in old-fashioned logistics: purchasing, warehousing, picking, packing, shipping. Almost all of the remaining work will be customer service: returns, fixing mistakes, handling late deliveries and billing issues, etc.
Now add a web site to place and track orders to the business. It is a tiny part of the work required to launch and doesn't change any of the back-end "brick and mortar" stuff.
Amazon has the infrastructure in place to do both the hard (logistics/fulfillment/customer service) parts and the easy (web site) part. If you think this is something you can crank out in a weekend with a Ruby on Rails book good luck.
Something that would be a valuable addition to this idea would be a way of starting out by making purchases on demand, and then being able to easily automate them if they are regularly occurring. For example, I don't pay attention to how often I actually need toothpaste, so right now I wouldn't want your service because I don't know how much toothpaste to buy, and how often I need to buy it. But I might want it if it tracked the toothpaste usage for me, and then I could automate it if it turned out to be a very regular need.
Amazon Subscribe and Save already offers this service: http://www.amazon.com/Health-Personal-Care-Subscribe-Store/b...