There are two answers to your question:
1. To see what you have marked as due today, you can use the "Due Items" perspective in the Perspectives menu. If you select that you will see what you have that is overdue, due today, and due soon. If you only want to see what is due today, you can collapse the other sections of the outline.
2. On a deeper level, though, the GTD approach emphasizes setting due dates only when they are real
due dates, not simply
"I'd like to get this done" dates. The method encourages you to decide what is most important and do that, instead of being driven by deadlines. Sometimes you can't avoid focusing on what is urgent (due soon), but the GTD methodology discourages you from focusing too much on it. Instead, you should use frequent reviews, flags (if you find them useful), and context lists to determine what is up for today. That might, in fact, be something that is due in a month.
For more on the GTD method, I recommend Merlin Mann's
43 Folders blog, and especially the entry
"Getting Started with Getting Things Done." OmniFocus was designed with GTD in mind, and though it can be used without strictly adhering to the GTD method, understanding GTD will give you insight into why the application is set up as it is.