Blender has an enormous collection of hot keys. Some of them are reminded in the ToolBox, a complete listing is added below.
(A showcase file of this page is included in the manual download).
 

STANDARD HOT KEYS (ALL WINDOWS)

F1    load blender file
SHIFT     F1    load as library from blender file
F2    write blender file
F3    write image

SHIFT    F4    window: Data select
SHIFT    F5    window: View 3D
SHIFT    F6    window: Ipo
SHIFT    F7    window: Buttons
SHIFT    F8    window: Sequence
SHIFT    F9    window: Schematic Diagram
SHIFT    F10    window: Image
SHIFT    F11    window: Paint
SHIFT    F12    window: Image Select

F11    show image (toggle)
F12     render

        Button window is also global:

F4    lamp buttons
F5    material buttons
F6    texture buttons
F7    animation buttons
F8    world buttons
F9    edit buttons
F10    render buttons 
 

Arrow left    minus 1 frame
SHIFT    Arrow left    first frame
CTRL    Arrow left    previous screen
Arrow right    plus 1 frame
SHIFT    Arrow right    last frame
CTRL    Arrow right    next screen

Arrow up    +10 frames
CTRL    Arrow up    window full (toggle)
Arrow down    -10 frames
CTRL    Arrow down    window full (toggle)
 

TAB    enter/exit edit mode

ALT    A    play animation
ALTSHIFT    A    play animation in current window + all 3D windows

I    insert key (each window diff. menu)
J    spare page render window

N    number buttons
CTRL    O    open file
CTRL     U    save user defaults
CTRL    W    write file
CTRL    X    erase all (= load user defaults file)
Z    zoom, in render window
 

VIEW 3D WINDOW
 

SHIFT    TAB    in text edit: a tab!

PAGEUP    Next Object key
PAGEDOWN    Previous Object key
HOMEKEY    'home', show all visible objects

' (ACCENT)    all layers
~(TILDE)    restore layers 

LEFTMOUSE    cursor / gesture / vertex paint
CTRL    LEFTMOUSE    add vertex
MIDDLEMOUSE    trackball
SHIFT    MIDDLEMOUSE    translate view
CTRL    MIDDLEMOUSE    zoom view
RIGHTMOUSE    select (vertex paint: sample color)
SHIFT    RIGHTMOUSE    extend select
CTRL    RIGHTMOUSE    centre select

SHIFT     A    add menu
CTRL    A    apply
A    (de)select all

SHIFT    B    render border
B    border select
B-B    (in edit mode) circle select

CTRL    C    copy menu
ALT    C    convert menu
SHIFT    C    home & cursor op zero
C    in edit mode curves: cyclic
C    window center to 3D cursor

SHIFT    D    add duplicate
ALT    D    add linked duplicate
CTRL    D    display image wrap as wire 

E    extrude mesh / nurbs

F    Face select on/off
SHIFT    F    Fill mesh
ALT    F    beauty fill
F    make edge / face or connect curves

ALT    G    clear position object 
G    grabber

CTRL    H    in edit mode curves: automatic handle type calculation
SHIFT    H    in edit mode mesh: hide deselected vertices
SHIFT    H    in edit mode curves: handle type 'auto'
H    in edit mode mesh: hide vertices
H    in edit mode curves: handle type 'align' or 'free' (toggle)

CTRL    J    Join objects

SHIFT    K    vertex paint: clear all.
K    draw Object Keys. (toggle)
 

CTRL    L    make link menu
SHIFT    L    select link menu
L    in edit mode: select Linked vertices
    otherwise: make local menu.

M    Move to layer

CTRL    N    recalculate normals, right-hand faces

ALT    O    clear origin

CTRL    P    make parent
CTRL SHIFT    P    make parent without inverse
ALT    P    clear parent
P    in edit mode: separate

ALT    R    clear Rotation
SHIFT    R    in edit mode nurbs: select Row
R    Rotate

CTRL     S    in edit mode: Shear
ALT    S    clear Size
SHIFT    S    snap menu
S    Size
 

CTRL     T    in edit mode Mesh: convert to Triangles 
CTRL     T    make Track
ALT    T    clear Track
T    in edit mode 3D curve: edit tilt

CTRL     U    undo/reload in text edit
U    in vertex paint: undo
U    in edit mode: undo/reload original data
    otherwise: single User menu

V    Vertex Paint on/off
V    in edit mode: vector handle
ALT    V    image aspect in object size

W    special Edit menu
SHIFT    W    in edit mode: Warp
ALT    W    write videoscape

X    erase selected

Y    Split mesh

CTRL    Z    Zbuffer and recalculate draw type shaded
SHIFT    Z    toggle Zbuffer en draw type Shaded
Z    toggle Zbuffer en draw type Solid

NUMPAD:
/    local view
*    rotate view to match Object rotation
.    translate + zoom view to selected objects
0    camera view
CTRL    0    make camera view
ALT    0    restore last camera
7 1 3    top / front / right view
SHIFT    7 1 3    down / back / left view
4 8 6 2 rotate view
SHIFT    4 8 6 2 translate view
5    toggle perspective/ortho
9    force redraw/recalculation
 

IPO WINDOW
 

CTRL    LEFTMOUSE    add vertex

PAGEUP    Next key
SHIFT    PAGEUP    cycle keys
PAGEDOWN    Previous key
SHIFT    PAGEDOWN    cycle keys

A    (de)select all

B    border select

C    Center: snap current frame to selected

D    add duplicate

G    grabber

SHIFT    H    in edit mode curves: handle type 'auto'
H    in edit mode curves: handle type 'align' of 'free' (toggle)

J    Join selected keys/vertices

K    show Keys (toggle)

SHIFT    S    snap menu
S    size

T    ipo Type menu

V    in edit mode curves: vector handle

SHIFT    X    delete vertex key
X    erase selected
 
 

SEQUENCE WINDOW

TAB    enter / leave meta strip.

SHIFT     PADPLUSKEY    insert gap: 250 frs
SHIFT     PADPLUSKEY    insert gap: 25 frs
PADPLUSKEY    zoom in
 

SHIFT     PADMINUSKEY    no gaps (after current frame)
PADMINUSKEY    zoom out

HOMEKEY    'home', view all strips

SHIFT    A    Add menu
A    toggle (de)select all

C    change menu

SHIFT    D    add duplicate

G    grabber

M    make meta strip

X    delete selected
 
 

SCHEMATIC DIAGRAM WINDOW
 

A    toggle (de)select all

B    Border select

G    grabber

L    select Links to
SHIFT    L    select Links from

S    scale

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