I tweeted this link last night with the message that I'd be passing it along to my students in the spring, perhaps even testing them on it. It's titled "10 Words You Need to Stop Misspelling," which is funny because there's only 3 actual spelling errors they listed--wierd for weird, definately for definitely (though they missed the far more common, in my experience, defiantly), and alot for a lot. The rest are all usage errors--fairly common ones too, though I have no idea how some of them are happening.
For instance, when did loose become mistaken for lose? I've seen this error for a couple of years now, and Andrew Shields, on my Facebook wall, said he thought it was only his German-speaking students who had that problem. Nope, Andrew--apparently it's widespread.
The inability for some of my students to distinguish between "then" and "than" is also a pretty recent phenomenon, and it's also pretty freaking aggravating because the error throws off the whole meaning of a sentence at times (makes the writer look like a dumbass the rest of the time).
And when I get "weather" for "whether," I start drinking, because it's going to be a loooong paper to grade.