This week, the world celebrated Spreadsheet Day, AKA the most boring holiday devised by humankind. But wait! If you hate spreadsheets and everything they stand for, it probably means you don't know how to use them properly. Here are our most useful spreadsheet hacks for Microsoft Excel and Google Sheets; suitable for novices and experts alike.

If you're sharing or collaborating on a Google Spreadshet, you can now set columns to validate data types. Cells can enforce certain data types, require valid URLs or mandatory text, for example.

Techie Leonard Lin publishes his investment asset allocation in a Google Spreadsheet which employs the super-useful GoogleFinance formula for live-updating stock prices in-sheet.

Here's a tip for the Google Spreadsheet users out there. Google has added the ability to set alerts to notify you about new data as it is added. This will be useful if you work collaboratively and have shared your spreadsheet with others, or if you use forms to collect information from multiple users.At the top right of the Spreadsheet page you'll see a link to "Set Notification Rules" (or you can find it in the File menu). You can control
what parts of your spreadsheet to track, and how often alerts are sent. You can see the options in this screenshot:

Google expert Philipp Lenssen has come up with a brilliant spreadsheet that creates a world map coloured by how often a term gets Googled by country. Data nerds will love this: The sheet dynamically pulls in the number of results for a given search term and updates a map widget with colours representing the totals. After the jump, check out what the map looks like for a search for "lifehacker."

Google rolls out a few impressive new features to its online spreadsheets offering today, including cell autocomplete, iGoogle gadgets, and notifications about collaborative edits. Autocomplete works the way any desktop spreadsheet does: as you type, if the cell contents match a past entry, Spreadsheets will suggest the value. As for data collection and sharing, you already know you can ask others to fill in a spreadsheet with a user-friendly form. Now you can get notifications whenever a sheet gets updated, down to a specific range of cells or via a form. Finally, you can track the status of your spreadsheet on your iGoogle homepage by creating a data widget, which updates as your spreadsheet does. Pretty nifty. Google Spreadsheets Adds Gadgets, a Directory of Features

CNET blogger Dennis O'Reilly is using Google Docs to manage his NCAA basketball pool; the bracket spreadsheet he put together is public and free for anyone to copy and use.