Desk shortcuts
+ = Create a card
I = Toggle Inbox
D = Open calendar on Daily view
W = Open calendar on Weekly view
C = See completed work
⌘K = Search
Text editor shortcuts
⌘B = Bold
⌘I = Italic
⌘U = Underline
⌘D = Code highlighting
@ = Mention a card
[] or [ ] + Space = Checklist
With the desktop app
⌘⇧C = Quick card creation
⌘⇧H = Open Mindmesh from anywhere
With the desktop app and calendar integrated
⌘⇧J = Join the conference call
⌘⇧E = Create a card for next event
You can now customize your shortcuts from Settings >> Account & Settings >> Customize keyboard shortcuts