I'm graduated with an English degree and I've noticed a lot of companies I'm interested in require some business know how. I want to take some business courses but don't have enough time to attend college full-time. Would a business certificate from extension courses make the slightest difference on my resume, or is it better to simply get a bachelor degree from an online college? Or get an AS degree from a community college? I'm looking for the choice that would have the most impact on future employers.

Just take adult education courses in management, accounting, economics and/or finance. A lot of things can be done online. Local city and state run colleges are often less expensive and have flexible scheduling for working adults.

I would say at this point, a business certificate of extension classes would be your best bet-basically going back for post-graduate work.....meaning that you are taking a few classes not in an attempt to get a masters, but to improve your skills in the career world. I would take a few marketing classes if I were you. I have an english minor and am currently working in a marketing position while I am putting myself through grad school-and this job requires a lot of writing and my minor helped me get the job. Many marketing jobs require writing and of course your English degree would ensure that you are qualified for the writing aspect of the job, and a few classes would help show that you are learning about, and are interseted in pursuing further, a marketing career.
Good luck!