1. Attend conferences and seminars. Pure networking events are often boring. When you attend a conference or a seminar with a technical or business theme, not only will you be able to learn something out of your domain of expertise, but you'll be able to chat with like-minded entrepreneurs and potentially foster new ideas. NECINA is one such non-profit organization providing these types of entrepreneurship opportunities.
2. Step up and volunteer. Say your a technologist and would like to gain more marketing insights -- find an organization where you can contribute on the marketing and customer-facing side. Conversely, say you have an MBA background and would like to gain some tech chops -- find an organization where you can help develop and maintain its website. The beauty of volunteering is that the entry bar is often lower (e.g. you are often spared a formal interview process), it usually won't conflict with your day job and employer, and you will feel good about adding social value.
Don't just learn by reading a book. Learn by doing. Not only will you gain hands-on experiences in the field, you will get good advice and mentorship this way as well. Have you ever dreamed of having experts sit down and share their insights and experiences with you on a topic of your interest? Yes, this is a sweet dream. After all, you are no longer in school and you are not paying them. However, if you contribute to a course of their interest, they will often be more than happy to do the talk while you do the work. See, get your interests aligned, and here comes a win-win.
3. Plan your career transition. Compared to the above two options, this one is much risker and less feasible. After all, changing your full time job requires careful consideration and is not always feasible due to many constraints. You might be ready for the transition, only when all the following conditions are met: a) you have gained enough expertise in your current job are no longer as motivated; b) there is a new opening that you are qualified for, excited about, and can learn skills; c) if the new gig fails, you have fall-back plans.
Again, any radical transitioning involves a lot of risk. Why not reduce the risk by trying something part-time, as a volunteer? I have some excellent volunteer opportunities for you, on both business and technology tracks. Ping me and I will offer you the leads for free.
P.S. I am not a recruiter, and has no financial interest involved. How I do enjoy match making. :-)