Some quick key short cuts for everyone:

click and hold mouse wheel = orbit tool
Shift + click and hold mouse wheel = pan tool
O = orbit tool
H = pan tool
L = line tool
A = arc tool
C = circle tool
R = rectangle tool
B = paint bucket
S = scale tool
F = offset tool
Q = rotate tool
E = eraser tool
Ctrl while uesing eraser tool = smooth line
Shift while uesing eraser tool = hide line
T = tape measure tool
P = push pull face tool
Space bar = selection tool
Shift when using selection tool = add or subtract to the current selection
M = move tool
Ctrl when using move tool = move with a copy
Z = zoom tool
Scroll on mouse wheel = zoom tool

These are my most used shortcuts if I missed your favorite shortcut key(s) please post it for everyone.

 

I know there is a way to change these as well...
Not sure how, but I know I seen a way.

 

I asked Mark in a PM how to make Groups with a single keystroke, so he 'splained it in real small words to me, so I'm just posting it here for the rest of y'all to gaze in wonder. To assign a single keystroke to any function within SketchUp -
. . . go to "Window" in the top menu then select "Preferences". A window will pop up. In that window select "Shortcuts". At the top you will see a text box called "Filter": type 'group' in the box and it will filter for everything to do with groups from the list under it. There are only two options that come up "Edit/Close Group/Component" and the second one, "Edit/Make Group".
Select the "Edit/Make Group" and once you have it highlighted just add the letter you want to use as your shortcut to the right in the "Add shortcut" text field and click on the "+" sign to assign it. (Mark uses the letter "U") It will now jump down to the Assigned text field. Click ok and your done.
I chose to do it a little differently. First I found the "Edit/Make Component" command and UN-assigned the letter "G" from it. Then I used the letter "G" for "Edit/Make Group". I don't have any letter assigned to "Edit/Make Component", because there's already an icon to do that anyway.
Now, after selecting all the lines and curves(by select, click, drag a select box around them) then I just type the letter "G" (upper case not required) and Voila! it's a Group!

 

I too had changed the 'g' for groups. I don't know what they thought of when they assigned 'g' for component. All I know I'd like to smoke some of it too.

Also, shift 'z' is for zoom all. It's default in SU.

I added two shortcuts:
Shift 'a' for unhide 'a'll
Shift 'h' for 'h'ide