I'm a self taught programmer with 6 years of professional development experience. Due to only having an Associates of Arts degree, the "education" portion of my resume is bare. I already have a professional skills section so I think including those in the education section would be redundant. What are some ways in which I could expand this section?
Don't bother. The opportunity cost of going to school is too high. Experience and knowledge is more important.
There has been a lot of debate on the programmers section of this site. There's generally two opinons. One is that they are great, the more papers you have to your name the more attractive you are to your employers. The second is that they are a waste of time, and are a signal of someone who wants to 'get the job and cruise'. I've seen both of these attitudes. Generally, the more nimble startups and very focused shops don't pay any attention to certification in my experience, whereas large enterprise will appreciate them (though to varying extent).
As long as you have some university degree, 10 years into your career it won't matter what the field was. If you can talk about things you've done, things you know, and things you can contribute, that will matter much more.
Don't get me wrong, it would be IDEAL for you to have a comp sci degree if you want to be a developer, but now that you don't, it's better to invest your time doing other things.
What to do instead:
1) Learn new/tomorrow's frameworks and technologies.
2) Read books/learn general theory. Go through data structures, algorithms, design patterns, etc.
3) Participate in open source / build something of your own. Put that experience on your resume.
The things above will serve you much better than sinking 3-4 years of your life and un-earned income into schooling. IMHO you will honestly learn more. It might also do more for you than sitting through power-point slides of online accrediations.
Finally, there' something to be said for self-taught developers. When you have a guy from general arts that did a lot of work to go into programming you know this person is passionate and interested in it. You also know that they were/are willing to learn and aren't 'done' with their professional development (IMHO developers who are 'done' learning should get out of the biz).
Thought I might as well turn this into an answer (originated from comments).
I'd look at becoming certified in the technology or areas you're already familiar with. Since this is off your own back, you'll probably want to be looking for the cheaper certifications. I know you can do some certifications (or at least parts of them) for free through Microsoft on their technologies.
Go to School
Credit goes to Scaaahu. Distance learning may sit well with you. Here in the UK we have the Open University, which allows you to study at a number of levels on a flexible schedule (and reasonable cost), though this would take more time since each course has assignments, deadlines, etc.
What are some ways in which I could expand this section?
The simple answer is, "Don't". If you have several years of experience already, your education is becoming less and less important by the year. Why fix something that isn't broken?
Instead of beefing up education, beef up some of the other sections. Do you have a GitHub account or other publicly-accessible code to point people to? How about a Stack Overflow account where people can read your questions and answers? Do you participate in meetups or user groups, projects outside of work? Do you blog on tech topics or attend conferences?
If you have been in the industry for 6 years, you obviously are able to get a job and keep one. Why is your education now a concern for you? Sounds like you will be looking for a job, in which case see all my suggestions above for fattening up the resume and making yourself attractive to employers. Your lack of education hasn't hurt you yet, so you may have nothing to worry about.
Regarding certifications, I coincidentally published a blog post on this very topic today. If you are considering taking the advice of those in this post that suggest certs, consider reading "The Stigma of Tech Certifications (and their real value)".
Most of us only have one or two lines on the resume in the education section. BA in X from University Y in YYYY. They don't have paragraphs describing the course work and the projects.
If the job requires a bachelors, you don't have one, so there is no getting around it. Some positions will require 10 years experience, or bachelors plus 5 years experience, or masters and ...
If the resumes are being filtered by software you might never make it through the filter without having the bachelors. But there are other cases where you can bypass the filter. Apply directly to smaller companies. Use friends and coworkers to recommend you for positions.
Take advantage of what education options exist in your employer. Some will pay for a degree, others will repay your for X$ a year for classes related to your job. Just make sure you bill them for ones that help you get your degree.
Otherwise use the rest of your resume to show your depth and breadth of your experience, thus minimizing the lack of a bachelors degree.