Spaces is a great way to keep your screen from getting too cluttered. But if you like to keep applications in specific window positions, it can be a hassle to move them from one space to another, because those window positions can be lost. Mac OS X Hints reader rab777hp found a fix, a way to move a window from a specific spot in one space to the same spot in another:
All you have to do is enter Exposé from the Spaces overview, and then move the window from one space to the other. Once you exit Exposé, you'll find the window occupying in the same location on the new screen that it had in the previous one.
On my MacBook, on which I still have the default keyboard settings, that means I'd press F8 to get into the Spaces overview and F9 to invoke Exposé in All Windows mode. I'd then move the window from one space to another, and finally press F9 again to exit Exposé.