Free Excel help article on Microsoft Excel keyboard shortcuts.

Navigating within a worksheet
Keyboard shortcut                                          Action
Tab, ->                                                             Skips to the next cell on the right
Shft+Tab, <-                                                    Skips to the cell on the left
?                                                                     Move one cell up.
?                                                                     Move one cell down.
Ctrl+->                                                             Move to the last occupied cell of a row of data
Ctrl+<-                                                             Move to the beginning occupied cell of a row of data
Ctrl+?                                                            Move to the first occupied cell of a column of data
Ctrl+?                                                            Move to the last occupied cell of a column of data
Ctrl+Home                                                      Move to the first occupied cell of data
Ctrl+End                                                          Move to the last occupied (bottommost) cell of data
Ctrl+.                                                               Move clockwise to the next corner of selected range

Navigating between workbooks
Ctrl + Page Down                                            Move to and activate next worksheet in workbook
Ctrl + Page Up                                                Move to and activate previous worksheet in workbook
Shift + F11                                                       Insert new worksheet to left of active worksheet

Show or hide columns and rows
Keyboard shortcut                                          Action
Ctrl+0                                                              Hide current column
Ctrl+9                                                              Hide row column
Ctrl+Shft+9                                                     Unhide current row
Ctrl+Shft+(                                                      Unhide rows within the current selection
Ctrl+Shft+)                                                      Unhide columns within the current selection

Selecting contiguous cells
Keyboard shortcut                                          Action
Shift + Directional Arrow                             Select the cell(s) in that direction (left, right, up, or down)
Ctrl + Shift + Directional Arrow                    Select to the last occupied cell in that direction (left, right, up, or down)
Ctrl + Shift + End                                           Select from active cell to last occupied cell that is down and to the right
Ctrl + Shift + Home                                       Select from active cell to first occupied cell that is up and to the left
Shift + Backspace                                         Collapse cell selection to just active cell
Ctrl + A                                                          Select all of the occupied cells in current range; press again to select all cells in worksheet
Ctrl + Space Bar                                           Select all cells in current column
Shift + Space Bar                                          Select all cells in current row
Ctrl + Shift + + (plus  sign)                            Insert new row – select row first
Ctrl + – (hyphen)                                            Delete selected row – select row first
F8                                                                   Turn on extend-selection mode; use directional arrows; F8 or Esc to exit extend-selection mode

Find, Replace and Go to
Keyboard shortcut                                          Action
Ctrl + F                                                            Open Find dialog box
Ctrl + H                                                           Open Replace dialog box
Ctrl + G or F5                                                 Open Go To dialog box

Cell Commenting
Keyboard shortcut                                          Action
Shift + F2                                                         Add new comment; edit cell comment
Ctrl + Shift + O                                               Select all cells with comments

Naming cells and ranges
Keyboard shortcut                                          Action
Ctrl + Shift + F3                                              Open Create Names from Selection dialog box; select cells and labels first
F3                                                                     Open Paste Name dialog box
Ctrl + F3                                                          Define name; open Name Manager dialog box (in Excel 2007)

Working with formulas and functions
Keyboard shortcut                                          Action
Shift + F3                                                         Open Insert Function dialog box
Ctrl + A                                                           Open Function Argument dialog box – when insertion point is to the right of function name and (
Ctrl + Shift + A                                               Insert parenthesis () and function argument names – when insertion point is to right of function name
F2                                                                     Edit formula in cell; insertion point is at end of cell contents
F3                                                                     Opens Paste Name dialog box
Alt + =                                                             Inserts AutoSum formula
Highlight Portion of Formula + F9            Evaluates selected portion of formula; press Esc to return to editing
Ctrl + ` (single left quotation mark)         Toggles between showing formula and formula result
Highlight Portion of Formula + F4            Cycles between absolute, mixed and relative references for highlighted cells