While there is no shortage of technologies to allow for online ordering, there are a few general types:

1) Secure email forms - for simple online purchases, not requiring a shopping cart. This involves a secure web site, coupled with secure email. It can be effective and inexpensive - a good example of this system is at a site I designed

, Napa Valley Bike Tours (this is the reservation form)

2) External Web-based storefronts - these can be quite sophisticated or relatively simple, and have the advantage of letting someone else worry about the security of orders and updates. Examples of this would include Nexternal and Yahoo!Small business. I have helped to setup a number of Nexternal stores - these are especially popular with wineries, as they are sophisticated enough to handle the vagaries of reciprocal states, etc.. These storefronts are hosted on other systems, with your website handing ordering off to them (transparently to the user in most cases). An example of this system is at Anderson's Conn Valley Vineyards

3) Local Server Storefronts - in this category are systems that reside on the same server as the website. I always try to use open source solutions, to assure portability and minimum cost. One such solution is OSCommerce. This solution is more involved than the external systems to setup, but the cost savings in commission and monthly fees can often make up for that difference.