Hotkeys

It's often stated that the golden rule of Blender is to keep one hand on the keyboard while you use the other hand to control the mouse. Here is a summary of what I think are the most important hotkeys and mouse gestures. You may want to print this page for reference. When you become more proficient in Blender you will want a fuller list of hotkeys - you will find this easily on the net. Note that 'LMB' means left mouse button etc. Many of these manipulations need to be followed by a LMB-click to confirm (use RMB-click or ESC to cancel). If you are not sure how to do something try pressing the space bar and doing a search e.g. for 'extrude'.

Views

Numpad 7 = top view
Numpad 1 = front view
Numpad 3 = side view
Use Ctrl with the above to get the opposite view e.g. Ctrl+Numpad 7 = bottom view
Numpad 0 = switch to / from camera view
Numpad 5 = toggle between perspective and ortho views

Navigating

LMB-click = Place 3D cursor (where new objects will be placed)
MMB + drag (in 3D window) = orbit
MMB roll wheel = 'zoom view' (actually it really means moving eye forward or back for a zoom would imply a changing angle of view with eye in fixed position)
Shift+MMB drag = pan

Selecting

RMB-click = Select
Shift RMB-Click = add to /subtract from selection
B = Box select (everything inside the box and everything the box touches will be selected)
BB = paint select (try it!)
Ctrl+LMB drag = lasso select (rarely used?)

G, R, S (note that you can also use the 3D manipulator for these)

G = 'grab and move' (should really be called 'translate'
GX (etc) = grab and move along X axis
G then MMB = grab and move constrained to closest axis
Ctrl+G = jump in steps equal to the width of the smallest grid squares you saw when starting the operation (you can zoom during), shift for more precision, ctrl+shift to snap to tenths of grid boxes
R = rotate (RX = rotate around X axis etc) R with MMB = rotate constrained to one axis
S = Scale (can use number, so SX5 would scale times 5 along x axis)
(avoid this, unconventional)) RMB-drag (in 3D window)= same as G
~~(avoid this, unconventional) RMB-drag in curve (in 3D window)= same as R~~

Other

A = unselect all / select all
E = extrude
F = Make Edge / face
I = insert Keyframe
K = cut
M (in Object mode) = move to new layer
M (in Edit mode) or Ctrl+M (in Object mode) = Mirror e.g. MX = mirror along X axis. This just flips the object - it is not the same as using the mirror modifier.
N = show/hide transform properties window
P (in Edit mode) make the selected faces into a separate object.
T = hide/show toolbox
W = ‘Specials’ menu (subdivide etc) or Boolean tools
X or Delete = delete
Z = toggle wireframe view

Shift+RMB =add to selection/make active/remove from selection
Shift+A = add something (same as using Add menu)
Shift+D = Duplicate
Alt+D (in object mode) = Link-duplicated. Objects that are link-duplicated are like instances of the same component in Sketchup. When you modify one object in edit mode the linked object(s) is/are modified in the same way.
Shift+S = snap selection or cursor to grid/cursor/centre

Ctrl+A = clean the mesh??
Ctrl+G = add to group
Ctrl+N = recalculate bone roll
Ctrl+P = make parent
Ctrl+W = Ctrl+S = Save over – won’t actually save until and unless you confirm the overwrite
Ctrl+Up Arrow = toggle between expanded window and tiled windows

Alt+A = play animation
Alt+D = Make linked duplicate (a bit like components in Sketchup - when you modify one the other(s) get modified in the same way). Compare with Shift+S which makes an unlinked duplicate.
Alt+G, Alt+R, Alt+S = clear the translation, rotation, or scaling of the selection

Tab = toggle Edit mode on/off (this is sometimes the only way to leave edit mode i.e. Mode menu does not work)

F12 = render still image
F3 = save the rendered still image
Ctrl+F12 = render animation (always saves to hard disk)
F11 = hide/show render window
Ctrl+F11 = play rendered animation