If you already have a list of subscribers or steady traffic to your website then you can sign up with companies that specialize in drop shipping. Product that you dont have to stock but can offer to your customers. When a customer places the order you collect the purchase price then send the company thats doing the drop shipping your cost for the product and they ship it directly to your customer making it look like it came from you.
If you are just starting out with a business and dont have a current base of customers then you dont need to be signing up with drop shippers who ship for hundreds of other customers already. Some of the larger mail order firms have companies drop ship fro them but these are not companies who are shipping for hundreds of others in fact they may only be drop shipping for a few customers.
There a lot of companies out there who would love for you to sell their products online. They know that they would not have to ship anything until you get paid by the customer for the product. These companies dont know about drop shipping so you have to seek them out and educate them.
When I was selling full time on EBay, selling PC and Video games, sales started to decline so I did some research of products that were selling good. The 2 products that were doing very well were DVD Movies and Designer jewelry. I then entered the necessary terms into my software, Net Prospector 2000 and found over 140 jewelry designers. I then contacted all the matches and asked them if I could sell their unique jewelry on the internet and have them ship to my customers once the product was paid for. I also told them that this would be a good way to move some of their slower moving pieces.
Over 50 companies responded positively to this, they provided me with pictures, weights and composition of each piece. I Processed all payments and they just had to ship to my customers.