Usability First: Methods
http://usabilityfirst.com/methods/index.txl

Usability First

Abstract:

There are a variety of approaches to usability evaluation that you may choose to take. The methodologies can be divided into two broad categories: those that gather data from actual users and those that can be applied without actual users present. Of course the approach you choose to take must factor in variables such as the cost of evaluation, the appropriateness of the technique to your project, time constraints of the project, and the cost associated with the implementation and training of new users. Usability evaluations can be conducted at many stages during and after the design and development process. In choosing a usability evaluation method, cost is invariably a consideration. But it is important to keep in mind that the value of a usability evaluation needs to be calculated not only in time and materials involved, but also in terms of the impact on the end-users, especially considering the cost of losing return visitors to your website due to unusable design.