OK, the elephant in the room that no one is addressing is quality. Remember the question that drove crazy the main character in Zen & the Art of Motorcycle Maintenance? His search (as I recall) led him to conclude that you know it when you see it (or read it) but it may be elusive in definition.
Many people talk as if a blog is a requirement. Who needs another blog that doesn't sing for its supper?
Many respondees take you at your word that you just want a proofreader. I actually do agree with Michael's suggestion about Fiverr (although I might have gone fishing in a place with more trained professionals). And I certainly agree that certain computer programs can help clean up. We use them ourselves.
But I would like to caution all about this "anyone can blog" theory. Anyone probably can blog, but should they? Because most don't do it well.
And, in my experience, most entrepreneurs are happy with their providers because they are cost-effective and show up on time. Judging by the hundreds of executives I have worked for, most are not trained to be able to distinguish so-so from good. They are just happy to have black text on white screens filling a space (and without anyone bitching about overt errors.) Most of us can easily tell real bad from real good. And most, untrained as they are, can't tell you anything about your blog except whether they "liked" it or not.
You might think this is a rant. Yet if I was arguing the same on behalf of distinctions in software programmers or digital marketers or engineers, then many of you would stand up & salute.
Instead of recommending you to a proofreader (exactly what you asked), I am taking a step back to ask rhetorically what are you hoping to accomplish with this blog?
You can get a proofreader, a PR copywriter, a sales copywriter, a journalist, an editor and storyteller (content marketing, in today's parlance)... in my world these are all different types of professionals with different skillsets...and each category has different levels of quality inside the category.
If your blog is to be significant in your business you might need professional help: hiring someone to proofread is like hiring someone to wash your car when you don't realize you need a trained mechanic.
Maybe you do just need your car washed but this discussion might be useful to others as a general call for action. Your web site today is more than your business card: it's your window to the world.
The majority of businesses we have written for found working with us to be a process of self-discovery. The engine that drives their sales story is engine that should drive the language of their blog. From writing their humble blog, many of these entrepreneurs promptly went back and sharpened their own sales presentations, changed their sales material, borrowed our language and perceptions, and held meeting with salespeople to re-examine their target audience. Some even changed, at some expense, their company tagline.
Good writing starts with good thinking, fueled by the experience the writer brings (not only writing experience but corporate and industry experience).
Even the word "blog" sounds blah. Try saying it out loud and in front of a mirror. Or in French, as in "Tu blagues..."
The man who coined this word first turned the noun "weblog" into a verb: "we blog." He must have used a proofreader on that day when he really needed an experienced writer.