Wireframes are really good in the design stage of a website for getting an idea of the layout and feel of a website. They are good at communicating these ideas with the client/customer (if there is such one). When using a good wireframe tool/program, they are really easy to create.
My favourite is Mockingbird, and web-based wireframe tool developed with Cappuccino (an open source framework for building desktop-looking applications in a web browser). It has a nice layout, is easy to use, and contains plenty of powerful objects to add to your wireframe.
They have a free license which allows you to create one project and collaborate with one other user. I haven’t discovered the page limit of the project (I’ve created about 7 pages with no problems).