clipped from: mashable.com 
c - compose a new mail
/ - puts your cursor in the search box
k - move to newer conversation
j - Move to older conversation
n - next message
p - previous message
o or Enter - open a conversation
u - return to conversation list
y - archive a conversation
m - mute (archive and make all future messages from this conversation skip the inbox)
x - select conversation
s - star a message or conversation
! - report spam
r - reply to a mail
a - reply to all recepients
f - forward message
Esc - escape from input field
ctrl+s - save draft
control + b - Bold
control + i - Italic
control + l - Blockquote (when in HTML - mode only)
control + z - Undo
control + y - Redo
control + shift + a - Link
control + shift + p - Preview
control + d - Save as Draft
control + p - Publish Post
control + s - Autosave and keep editing
control + g - Hindi transliteration