=SUM(A1:A15)
Spreadsheets were originally just for math and accounting geeks, as far as I know.
In recent years, they have become the "poor man's database". I've used them as a database at least as often as a true spreadsheet.
You probably own a spreadsheet already - either MS Excel or Mac Numbers. You probably don't own a dedicated database program like MS Access. That always costs extra.
If you haven't tried Google spreadsheets yet, you should. They work just like Excel and Numbers, basically.
Even if you never use a spreadsheet as a spreadsheet, you'll find many uses for it as a database. You just use it to keep track of stuff in an organized format.
You don't have to learn all the formulas and stuff that very few people ever use anyway. The only formula I know off the top of my head is the addition (SUM) one up above. More than that isn't really worth knowing.
So today you can get a little geekier again without anyone knowing. You don't have to wear a pocket protector while learning about spreadsheets...unless you really want to.