OS X Lion - The cursor reflects the fact that a window cannot be resized in a certain direction.
Tumblr - When the number of tags exceeds the width of the post in the dashboard, a horizontal move cursor appears and the list can be dragged to reveal the rest of the tags.
Windows 7 - Multiple monitors that aren’t aligned cause the cursor to stop at the corners, but only if you are moving slowly.
/via Colin Dabritz
Chrome - Status bar shift down with the cursor when it is hovering a link near the bottom of the page. After a few seconds its hows the entire URL.