Command/Control Shift R - Export to .swf/.spl/.gif/, and so on
Command/Control Shift O - Open as Library
Command/Control 1 - View movie at 100% size
Command/Control 2 - Show Frame
Command/Control 3 - Show All
Command/Control L - Show/Hide Library
Command/Control M - Modify Movie Properties
Command/Control E - Toggle between Edit Movie and Edit Symbol Mode
Command/Control Shift L - Show/Hide Timeline
Command/Control Shift W - Show/Hide Work Area
Modifying and editing
Command/Control G - Group
Command/Control U - Ungroup
Command/Control B - Break Apart
Command/Control Shift V - Paste in Place
Command/Control D - Duplicate
Command/Control A - Select All
Command/Control Shift A - Deselect All
Command/Control Shift O - Optimize Curves
Command/Control K - Align Window
Command/Control Shift S - Scale and Rotate
Command/Control Shift Z - Remove Transform
Command/Control Up Arrow - Move Ahead
Command/Control Down Arrow - Move Behind
Command/Control Shift Up Arrow - Bring to Front
Command/Control Shift Down Arrow - Send to Back
Command/Control T - Modify Font
Command/Control Shift T - Modify Paragraph
Command/Control Left Arrow - Narrower letterspacing (kerning)
Command/Control Right Arrow - wider letterspacing (kerning)
With the arrow cursor:
Control + Drag - Duplicates a shape
Press the control key first (Mac OS and Windows) and drag a selected shape or group of shapes to duplicate those shapes where you release the mouse button.
Command/Control Clicking a keyframe to move frame
Command/Control clicking a frame in the timeline switches the cursor to a slider. It allows you to drag that frame to a new place in the timeline within that same layer. This function is useful for editing the positioning of tweens, and so on, in the timeline.
With the magnifier tool:
Control + Click - Toggles to the opposite magnifier.
If the + magnifier (zoom in) is active, and you hit Control while clicking, you switch to the - magnifier and actually zoom OUT.
With the dropper tool:
Shift + Click - Select a color for both fill and outline tools
Clicking a red fill does the same, giving you the Bucket tool, and switching fill colors to red. But the outline tool colors are not changed. Clicking text switches the text tool to that color, and gives you the text tool. Shift clicking with the dropper makes the color you click active for ALL tools. It doesn't automatically switch you to any tool. It leaves the dropper active.
This shortcut is one of the least known for Flash. It's the only way to use the dropper on an outline for example, and then switch to the fill tool and have that color automatically active.