A co-worker recently told me that she needed to create a flowchart but didn't have Visio. She knew that I had it, but I played dumb. I told her how I'd recently learned to make simple flowcharts in PowerPoint, and recommended that she try that, but she needed more of a swimlane diagram, which would have been difficult in PowerPoint.
I then remembered that she and I had both recently received an Excel spreadsheet with some fairly complex workflow diagrams, one of which had a swimlane-like arrangement. Looking at it, I saw that I could select and drag the boxes and arrows, but I didn't see how to add new ones.
It turned out to be so obvious that OpenOffice's Calc spreadsheet program does it the same way: Select Toolbars from the View menu, then Drawing from the cascade menu. This adds a toolbar at the bottom with far more choices than you need. You can use this toolbar to add labeled boxes and arrows connecting these boxes to a blank spreadsheet or to a spreadsheet that already has numbers and text on it. The first time I tried this, the guy sitting next to me on the airplane—who hadn't said a word to me the whole trip—said "I've never seen flow charts in Excel before!"
On the Excel toolbar, the little square with the letter "A" and some horizontal lines lets you create resizable labeled boxes on the spreadsheet, and the icon of an arrow pointing to the lower-right lets you create arrows on the diagram. Once you've created either, selecting and then right-clicking one of these displays a menu that lets you customize its appearance.
On Calc's toolbar, the plain blue rectangle lets you add a resizable box to your spreadsheet, and double-clicking your new box lets you add a label to it. The Calc drawing toolbar has no icon for arrows, but if you use the one for lines you can then right-click a line and add arrow heads and adjust other properties.
I thought that Visio was a big, slow, bloated program even before Microsoft bought the company. I guess we need it even less than many people think.