Thanks to a toot from the wise and opinionated Matt Wiebe (interviewed by some doofus about design, WordPress and other such nerdery), I can remind you that you don't need to put two spaces after a period in your writing:
Every modern typographer agrees on the one-space rule. It's one of the canonical rules of the profession, in the same way that waiters know that the salad fork goes to the left of the dinner fork and fashion designers know to put men's shirt buttons on the right and women's on the left. Every major style guide—including the Modern Language Association Style Manual and the Chicago Manual of Style—prescribes a single space after a period. (The Publications Manual of the American Psychological Association, used widely in the social sciences, allows for two spaces in draft manuscripts but recommends one space in published work.) Most ordinary people would know the one-space rule, too, if it weren't for a quirk of history. In the middle of the last century, a now-outmoded technology—the manual typewriter—invaded the American workplace. To accommodate that machine's shortcomings, everyone began to type wrong. And even though we no longer use typewriters, we all still type like we do. (Also see the persistence of the dreaded Caps Lock key.)
So to sum up the article, it's proper to use one space. Not as an opinion or if you feel like it - but it's the way it's supposed to be. Just like you're not supposed to use comic sans or have sixteen different fonts in twenty five different sizes and colours, you don't need to have two spaces after a period.