Shortcut keys differ between PC (Windows and Linux) and Mac not just in Second Life, but across applications in general. PC shortcuts are indicated in the tables below. For your convenience, here's a table showing how modifier keys for keyboard shortcuts translate between platforms:

PC	Mac
Ctrl	Cmd ⌘
Alt	Opt ⌥
Shift	Shift
Right-click	Right-click (Ctrl-click with a single-button mouse)

Movement

Walk forward	W or ↑
Walk backward	S or ↓
Turn left	A or ←
Turn right	D or →
Run	Double-tap W or ↑ (forward); S or ↓ (backward)
Always run	Ctrl+R
Jump	E or PgUp (Tap once)
Toggle flying	F or Home
Fly up	Hold E or hold PgUp
Fly down	Hold C or hold PgDn

View

Mouselook	M
Reset View	Esc
Look at	Hold Alt and click mouse to re-center
Zoom in	Ctrl+0
Zoom default	Ctrl+9
Zoom out	Ctrl+8
Zoom camera in	Alt+↑
Zoom camera out	Alt+↓
Orbit up	Alt+Ctrl+↑
Orbit down	Alt+Ctrl+↓
Orbit left	Alt+Ctrl+←
Orbit right	Alt+Ctrl+→
Pan up	Alt+Ctrl+Shift+↑
Pan down	Alt+Ctrl+Shift+↓
Pan left	Alt+Ctrl+Shift+←
Pan right	Alt+Ctrl+Shift+→

Communicate

Friends	Ctrl+ Shift+F
Local chat history	Ctrl+H
Look at last speaker	Ctrl+\
Gestures	Ctrl+G
Previous message entered*	Ctrl + ↑
Next message entered*	Ctrl + ↓

*Available in Nearby Chat, Group Chat, and Instant Message windows.

System

Undo	Ctrl+Z
Redo	Ctrl+Y
Cut	Ctrl+X
Paste	Ctrl+V
Duplicate	Ctrl+D
Select all	Ctrl+A
Deselect	Ctrl+E
Close window	Ctrl+W
Close all windows	Ctrl+ Shift+W

General

Preferences	Ctrl+P
Help	F1
Search	Ctrl+F
World Map	Ctrl+M
Mini-map	Ctrl+ Shift+M
Teleport home	Ctrl+ Shift+H
Inventory	Ctrl+I
Build	Ctrl+B
Upload image	Ctrl+U
Take snapshot	Ctrl+ Shift+S
Quit Second Life	Ctrl+Q

For advanced users

It is possible to remap the Second Life Viewer's keyboard controls, but be aware that the procedure is risky and can compromise the Viewer's functionality. To learn more, read our wiki article on Keyboard mapping.