The new interface of Gmail has some useful keyboard shortcuts for composing messages.
<Shift> + <Esc> : focus the main window
<Esc> : focus the latest chat or compose box
<Ctrl> + <.> : advance to the next chat or compose box
<Ctrl> + <,> : advance to the previous chat or compose box
<Ctrl> + <Enter> : send message
<Ctrl> + <Shift+c> : add CC recipients
<Ctrl> + <Shift+b> : add BCC recipients
<Ctrl> + <Shift+f> : add custom from
These shortcuts are displayed when you mouse over some buttons from the rich-text editor:
<Ctrl> + <Shift+2> : insert emoticon
<Ctrl> + <Shift+7> : bulleted list
<Ctrl> + <Shift+8> : numbered list
<Ctrl> + <[> : indent less
<Ctrl> + <]> : indent more
<Ctrl> + <Shift+l> : align left
<Ctrl> + <Shift+e> : align center
<Ctrl> + <Shift+r> : align right
