Add Shift to a movement key and Excel selects everything between where you started and where you land.
- Shift+Arrow adds one cell in that direction.
- Ctrl+Shift+Arrow (Mac: Cmd+Shift+Arrow) selects to the edge of the data.
- Ctrl+A (Mac: Cmd+A) selects the current table; press it again for the whole sheet.
- Shift+Space selects the whole row.
Start with Ctrl+Shift+Down: from the top of a column, it selects every value down to the last row. Combine it with Ctrl+Shift+Right to grab a whole block.
The selection always keeps its starting cell as the active cell (the white one), so you can see where you began. The status bar at the bottom shows the Sum, Average and Count of what you selected.