Mac OS X Lion Pocket Guide – O’Reilly Media
Resize from Any Edge
In previous versions of OS X, windows usually had resize handles in their lower-right corners. In Lion, those handles are gone and you can change a window’s size from any edge. To pull this trick off, just hover your cursor over the edge of a window and the cursor will change to a double-headed arrow; simply drag to resize the window.
NOTE
You’ll still see the occasional resize handle in programs like Microsoft Word, for example. Don’t worry: you can still resize such program windows by dragging any edge, though the resize handle works, too.
If you’re used to moving windows by grabbing an edge and dragging, that won’t work in Lion—you’ll simply resize the window. You’ll have to adjust your habits and click inside the window to drag it.