One of the extremely good "trends" that the whole cliche'd web 2.0 wave has bought us, is thinking of how the user is going to be using the site.
Often when you're caught up in the middle of code, or trying to slot in a dozen pieces of data into a content page, the big picture can be lost. An excellent way to deal with this is to write down the primary goals of each feature or page. Don't go into too much detail or you'll never bother to do it, but for example, a page that allows you to sign up for a free email address.
What do you want people to do? Sign up of course! This is the primary function of the page, but there is also a secondary function, making it clear where users should login.

Lets use the popular webmail service "hotmail" as an example. They've got a very clear login box, full marks for the secondary function of that page. The registration however, I feel could be improved, although it certainly isn't bad. The faster you can get a user to start the signup process, the better - especially with well branded sites which don't require all that much marketing waffle when people already know what they want, and just want to know the easiest way to do it!
You could very easily move the marketing/explanation information down further for those who need more convincing, and use the top 1/5th of the page for the large number of people who just want to get it done (click the image to enlarge).