Google Spreadsheets can autofill cells with sequential numbers and other related data, like rivers and countries. It's still not an advanced Excel, but this feature can save you some time when you're numbering a column.

This feature works with both rows and columns. For example, start out by numbering your column with 1, 2, and 3 in three cells next to each other. Then select those three cells and move your cursor the the bottom right-hand corner of the selection. (You should see a blue dot.) Hold your Ctrl key (Alt/Opt on Mac), then click and hold the dot, and drag your cursor down—or across if you're filling in rows. (Note: This isn't strictly necessary with numbers, but with related data like countries, it is.)

It works for sequential numbers (1, 2, 3...), even numbers (2, 4, 6...), and more. Adding to the niftiness of it all, you can also autofill countries, car manufacturers, and other related sets of data. Try it out, and we'd love to hear about any other sets of data that you come across that this autofill works for.