It sounds like you've got a few factors working against you:
Age - you've simply spent fewer years on this planet than the average college graduate. Worse yet, you look younger than you are, making the age factor even more significant.
Easily quantifiable experience - you've got experience and knowledge, but it's not as easily quantifiable as a person with a degree and a GPA.
Selectivity - the best description of this quality that I've ever heard of was Joel on Software (see link, p. 154 the bottom of the page) when he talks about the idea that someone who was vetted by something relatively exclusive and in high demand creates an impression that the candidate is someone special.
Over time, some of these factors will change - you'll get more and more experience, you'll get older and older and you'll look older and older. But the idea here is to find you a match to a job now.
Here's some thoughts on how to combat some of these factors.
Age and the Vision of a Young Person
Ender's link is pretty good for this. Anything you can do in person with your dress, your mannerisms, and your general attitude to brand yourself as someone with the appropriate experience is a good thing.
Prior to appearing in the interview, do everything you can to let your work speak for you. While this is true for everyone, I'd say it's extra true for someone fighting the stigma of a less traditional background:
- Make sure your resume is spotless - no typos, no strange grammer, very clean and easy to read.
- Have examples of your work that you can provide BEFORE you appear in person. Let the first impression be your excellent work, not your young face. Provide the ability to view this work before you appear in person.
Make It Easier to Quantify your Experience
Years of experience doing freelance, languages learned, certifications earned - anything that could be understood by a search engine is a real win here. When you're applying for a large company job these days, it's generally true that a computer will see your resume long before a person does.
In any area where you have demonstrated profound talent or a case of high-selectivity (even if it is unusual) - make it clear. "I was the only one of 100 candidates to be given the opportunity to..." is a great topic for a cover letter. "I contributed to a full lifecycle of project X" gives a sense of longevity that shows that your claim of experience is well-earned. These phrases are generally not search-engine friendly, but they make it clear to the person reading the resume just why the work you've done makes you the equivalent of a college grad.
It may take a Rare Opportunity
It may be that the right opportunity is as unusual as you are, so get creative in the hunt. An enormous organization with a lot of applicants is more likely to have strict rules and enough opportunity to hire others that they don't need to take a risk. Several organizations I've worked in simply won't consider a graduate without a certain caliber of college degree - the reasoning is, if they get 100 applicants for 20 positions and they find 20 talented and qualified college grads with minimal effort - then why take the risk?
What you want in an opportunity is an organization that isn't thinking that way - one that values your unique experience. This can come from personal networking, or looking at organizations that aren't as large or aren't so entrenched in their recruiting practices.
Make sure of Your Non-Technical Skills
I'm not here to sell college educations - but this is the part where I talk about the value of the college education with the point that you want to make sure that when you say "I'm the equivalent of a college grad in the value that I can offer a company" that you are correct and capable of selling the idea.
Many times when I talk to technical people, I hear the theme that they could have learned all the technical skills just as easily (and for far cheaper!) by self-learning. They are probably right.
What I've seen in observation, however, is that there's a couple other factors in college life that help in the workplace. Here's my list:
Time spent on teams - It really doesn't matter whether it's a school project, volunteer work, or a hobby, club or activity - when people get together to something hard enough that it takes multiple people, they learn about how to get things done together. Communication skills grow, negotiation/compromise skills develop, and people learn more about themselves as members of a team environment. The only way to develop team skills is to be on teams. There's plenty of books on it, but it's an art that has to be practiced.
Traditional written and verbal communication skills - engineers for the most part aren't great writers. But an engineer who graduated college has been forced to write well enough (at least a few times) to pass courses with writing requirements. Similarly, most have had to speak in public enough that they can form a coherent thought and make a case clearly and succinctly. Mileage varies on which language is expected. I've noticed that in recent years, most college grads from India speak quite clear English and write well enough to be understood. I can't say for sure whether this is a baseline within India, as most of my experience has been with engineers who were educated in India but are now working in the U.S. and have been for some time.
Able to perform in a fixed schedule, receive and respond to feedback, and juggle competing priorities - there's a certain level of conformity expected in a college environment. People have to manage to attend classes on time (mostly), respond to the feedback provided in graded assignments in a constructive way, and deal with competiting priorities. Needless to say - college isn't special, but I have seen cases where the reasons college was a bad fit for an individual was one of these factors. That's fine - but for some companies, these are ALSO key elements of success in the corporate world.
There's two parts to this section. First, you need these skills and experiences if you're going to claim "the equivalent of a degree" when you write your resume and sell yourself. Second, you need to be able to sell the idea when you submit your resume for a job. This doesn't have to be a case of demonstrating skills on the job or in the class room. For example:
- If you do large scale volunteer work or a challenging, team-oriented hobby with some degree of intensity - you can highlight team skills.
- If you have written reports or have other examples of good communication skills - you can include them on your resume - whether or not they are technically related.
- If you have conformed to rigid schedules, complex priorities and a structured environment, you can either highlight on your resume or speak to it in your cover letter or interview.
My thought is that there is very likely a double standard. If you have a friend who is a lot like you except he's a college graduate - it's quite likely that interviewers are looking at your friend and cutting him slack when he's weak on some of these softer skills. But where they are probably thinking "this guy isn't a college graduate, can he really handle working here?" then a small slip in the soft skills confirms a negative impression. Fair or unfair, it's a possibility.