One bit of advice if you're using hollywood's suggestion: be sure you don't have the Status Filter set to anything with the word "due" in it if you are looking out beyond the "due soon" period (defaults to 2 days, set in the Dates & Times part of the Data preferences). Also, for the best results you should view your tasks in Context mode, not Project mode.
For an even more powerful approach, check out RobTrew's
Where in OF script, which will allow you to do a search such as:
tasks where (due date ≥ date "2/11/11") and (due date ≤ date "2/13/11")
(to see if there is anything due on that day or shortly thereafter)
or even a more complicated search like:
tasks where ((due date ≥ date "2/11/11") and (due date ≤ date "2/11/11 2:00 PM")) and (estimated minutes > 120)
(do I have anything due before 2PM that day that will take at least 2 hours?)
Finally, one last little "gotcha" to be aware of when trying to decide how much work there is to do on some future date: if you have repeating actions, only the next repeat is present. If you had an action to do some lengthy task at 1 PM every Friday, none of these methods would reveal it until you complete the previous one on 2/4/11. OmniFocus does not do repeating actions in the same way as iCal, where you can see them stretching out into the future. That's an argument for putting tasks that are really fixed in place on your calendar, and using OmniFocus to manage all of the other tasks that may have to be done by some specific date/time, but don't necessarily have to be done at some specific date/time.