A spell check could change many things. Just use meta-writing tools!

I just finished reviewing a writeup. It was full of spelling errors, sloppy sentences, and annoying spacing and syntax errors. Flat out ugly! It is simply not in the best interest of you to send a colleague hastily written stuff. This is not just true for "official" writing like memos, papers or theses; but also true even for your emails or instant messages -- IMHO. Here are some of the reasons:

1. (First) Impression is Almost Everything: This has become a rule of thumb for the modern society, but, it seems that we just forget it. When a reviewer reads a sloppily written document, the likelihood that (s)he giving a positive rating about your document is very close to zero. 
2. Your Writing is Who You Are Inside: What you write eventually originates from your who you are inside. If you are an organized well-disciplined person, this will reflect on your writing too. Writings of people who think clearly tend to have clarity and brevity -- both good features of writing.
3. Your Writing is Your Signature: What you write is legal and can be used for and against you! Even emails and instant messages are like that too. That's why the term "documented" is used for an evidence going in record. No sane person would want to be associated with an illegal piece of written material. 
4. I Write Therefore I Exist: In academia, writing is so important that without your written material you simply don't exist. No academic would be known if (s)he does not publish something written. Yet, you are associated with what you write. You don't want to be known/associated with badly written material, do you?
5. Annoying, Annoying, Annoying: It is so annoying to spend time on a colleague's obvious writing errors. A colleague/collaborator is not there to correct your writing errors, but rather to have an intelligent communication on ideas and insights. (S)he may help in rephrasing your sentences to express the ideas/insights better, not in correcting them.

All of the above are the reasons why a writer must be extra careful. So, what is the solution? How can we make sure our colleagues don't get annoyed or we don't put ourselves into a bad situation because of a writing error? Well, there is no 100% avoidance strategy for this. You just try to be careful or freaked about what you write to people. But, meta-writing tools help a lot. Here are some suggestions:

• Spelling Errors: These are the most obvious ones to fix. Just use a spell checker for God's sakes! Virtually every editor has such checkers. It is a shame to ignore such spell checkers and send a document to someone before doing a spell check.
• Formatting Errors: Go through every page of your document and look for obvious formatting errors. Things like figures/text going out of margin, blur figures, something not appearing properly, etc. Have somebody close to you review it quickly. Even your child or spouse could do it. If something is not appearing right, another eye should be able to see it quickly. It does not have to be an expert eye who understands the written material. 
• Grammatical Errors: If you cannot write well in English, use a professional editor to get your document corrected. And, don't think of the money you spend on this as a waste. It is actually money well spent. Also, in most cases, large institutions have support system (e.g., a writing center) to review and correct/improve your writing. Just get help from them. Either way, getting somebody else to help typically means that you will have to prepare your writeup well ahead of time to make the time for reviewing/improving.

Remember it is your document. You are the person writing it. So, spending an extra hour before sending it to others is not a luxury, it is a requirement for interacting with others.