There are a number of keyboard shortcuts that will help you navigate the interface.
R - Show your Science and Research Screen
S - Show the Galaxy - Star Screen
F - Show the Galaxy - Carrier Screen
G - Show the Intel
L - Show the Leaderboard
O - Show the Options
I - Show the Inbox
N - Show a New Diplomatic Message
C - Show Combat Calculator
H - Show the Help
Q - Toggle Quick Upgrade Mode
V - Toggle Ruler Mode
W - Waypoint Edit Mode
Z - Toggle the Minimap.
B - Toggle Color Blind Help
- and + - Zoom in and out.
E - Exit, Return to Account Homepage.
ESC - Hide the Current Screen, or cancel Carrier Orders
Hold the Up and Down Keys when adding a star to a fleets path to override the default fleet orders with Collect All and Drop All respectively.
Hold the Alt key when selecting a star or carrier in the map to jump to the controlling players Empire Screen.
Diplomatic Message Mouse Shortcuts
Left Click any star while a Diplomatic message is open to add a link to that star into your message. You can also type in the stars name wrapped in two square brackets, [[name]].
Middle Click any star while a Diplomatic message is open to add a link to that star's owner into your message.