One of the most important aspects of operating a website is the ability to convert random traffic into customers or other registered users. It's infamously difficult to get people to take a minute or two to register on a new site. After all, most people are already members of several social networks, they probably have accounts at at least one or two of the major retail sites and no doubt a smattering of other registrations. It's hard to convince them to sign up to yet another site.

There are two ways around this problem, both of which have their limitiations and strengths:

OpenID

In other words, people can use it as a register once, log in everywhere type of service. I have used it before and it works perfectly well. It is easily integrated into a good web platform like Drupal, or Site prebuilder. By implementing an OpenID log in, users no longer have to register on your website, they simply log in with their pre-configured details. Depending on your site's setup, you can simply pull the information you need from OpenID in order to register their account behind the scenes. Simple, and elegant.

The downside is that it only works for people who have already registered with OpenID - otherwise, they have to register as per normal.

Integrated registration

A more subtle approach is to integrate user registration into the primary functionality of the website. For example, if you are selling luxury cars then allow anonymous visitors to browse your site and add cars to their shopping cart. If they decide to actually make a purchase, it's no big deal for them to fill out their email address and provide a password as part of their order confirmation because they have already committed to purchase.

If your website does not rely on sales, but is something along the lines of a social site, where registered users contribute something - such as content, opinions and so on. Then alter the way in which registration is presented. Instead of having two steps to get started (in other words, register first, post second), combine them into one. Your landing page will present a "Get started" button that allows users to start posting content immediately. The difference being that, as part of their first posting, they will be required to provide a username and email address (in order to identify them as the author of the post). Again, they have already taken the trouble to write a comment or an article, or whatever, so providing a username and email address is not too difficult, since they now have a small vested interest (in the form of effort).

It might seem like I'm splitting hairs by going to so much trouble to make registration a part of the functionality of a site. But if you consider that most people only give a few seconds of their time to look at a page, the difference between a succesfully registered and contributing user and someone who decides it's too much trouble can be the few seconds it first takes to register.

To cover your bases, combining both registration methods might prove to be most effective...