I am thinking of getting the Chicago Manual of Style. Application is for an IT business–proposals and technical documents.
Is the CMOS sufficiently general, or is it more geared towards scholarly works?
Other suggestions?
I am willing to buy two but hesitant: “Never go to sea with two chronometers–take one or three.” 
You might also want to consider the Microsoft Manual of Style. I use that when writing IT related content.
Part of my work is a very specialised kind of technical writing, and what we use is the Chicago Manual of Style.
(Note that if I were writing the above sentence for work, one letter would be different. For my personal writing, I don’t follow American style in punctuation or spelling.)
Chicago is definitely a good basis. Are you writing for end users at all? Then I’d also recommend the Microsoft Manual of Style - it’s their own style guide for referring to any and all of the elements on a computer screen or in computer hardware, and is useful for enforcing consistency. If needed, you can also supplement that with Sun’s Read Me First: A style guide for the computer industry. There’s probably overlap between the two, but they’re both good resources.
A good choice is to also develop your own style guide, to be used in conjunction with whatever else you choose. For example, you might disagree with a recommendation in Chicago or the MS MoS - in this case, you add your own details to how it should be handled in your style guide. That said, I’m in a new position (nearly a year!) and haven’t yet put anything to paper yet for our in-house style guide. But, it’s just me, too, so it’s easy to keep our own departures in my head, so far.
I’ve been a technical writer (mostly in the software industry) for 10ish years, and these are the two that I use, in addition to anything else I’ve developed in-house.
I agree with all of the responses so far, and will just add that if you will be writing for government customers at all – and since you’re in Northern Virginia there’s at least a chance of that – you may also want to investigage the Government Printing Office Style Manual. I’ve been an IT tech writer in the federal contracting world for 12 years and only one customer has required the GPO style, but I keep a copy at my desk and find that it’s handy for consensus-type questions/issues.
Consider joining the Society of Technical Communication (stc.org), for a world of information. They used to have online acces to many style guides.
Consider it, certainly, but do so carefully before forking over the $215 that it is now. IMO, it’s not worth it.
The STC has a ton of good people doing good things, but as an organization I think it’s broken. I see too little accountability for those at the top levels of the organization and too little value provided for my money. And what value is provided is sometimes hidden behind extra costs and fees. The technical resources and information that I need I’ve been able to find on free websites that provide me a ton more necessary and needed data than the STC ever did. There’s a reason that they’re doing poorly, and it might be time to disband and start fresh.
I’m not knocking the people who belong to the STC - they’re doing good and valuable things - but the organization isn’t honestly listening to them. I’ve been a member for a number of years, but I didn’t re-up this year and I doubt I will in the future. There’s just not enough value there. (And I say this as being part of the problem - you only get out what you put in, and I certainly haven’t put in much at all, so I’m also to blame.)