The great thing about the academic experience is that it exposes you to many different tasks and experiences that are relevant to careers outside of the traditional tenure track. If you can identify the parts of your work that interest you the most (hint: these are probably the times when you're actually happy to be working rather than reading blogs), then you've already made a huge first step towards identifying your ideal career.
So: what do you enjoy most about your current situation? Straight-up lab work? Maybe a research position in industry would suit you. TAing? Maybe you'd like to be a teacher, or to work in a public communications role such as in a museum or science centre. Do you find yourself more drawn to the opinion pieces and corporate merger information than the research articles in Science and Nature? Consider a career in science policy, intellectual property, or business development.
Now find a way to do them more often
If you enjoy a specific part of your current position, find a way to incorporate more of it into your remaining time in academia. This is a good idea for two reasons
1) it gives you a better idea of whether you really do want a career that focuses on this one area2) it gives you experience that will make your CV stand out from all the others
You want to convince future interviewers that you're looking for a career, not a job; being proactive, not reactive; working to a long-term plan, not applying to any old scientific job that crops up in your local area. If you can point to areas of your CV that show a long-standing commitment to your chosen field (do this in the cover letter and - repeatedly - at interview), you will stand out from the pile of CVs stacked up in human resources.My postdoc supervisor knew that I eventually wanted a job in scientific communication, and she was happy to help me gain more experience. I volunteered to edit and proofread manuscripts and studentship / fellowship applications written by other lab members. I wrote parts of her grant applications and progress reports.
But don't just rely on your boss; look for other opportunities too. My department had a newsletter, run by some of the grad students, so I wrote articles whenever I had time. I volunteered for Let's Talk Science, an outreach programme that took us into high schools to, well, talk about science.Writing and communication are relatively easy examples, because they're such a large part of academic science anyway. But you should be able to find ways to gain more experience regardless of your chosen future field. Just volunteer for anything even vaguely related - even if you end up spending a lot of time proofing legal documents from your technology transfer department, sitting in committee meetings, volunteering for ethics review boards or whatever, you can find a way to get the right experience and flesh out your CV. (That's the other great thing about the academic experience; always more tasks than volunteers).
Again, you don't have to stick to academia - maybe a local charity would appreciate some help with their own newsletter or website. Maybe you have a friend who could use a fresh pair of eyes on her big sales report. The skewed tasks:volunteers ratio is not just an academic phenomenon...
Repeat ad infinitum
Hopefully the advice above will help you to make that first step into your new career. But don't stop now! Your first non-academic position is unlikely to be the amazing dream job that you will do for the rest of your life, but it will expose you to another, broader, range of experiences. For example, as well as the grant writing that is my day-to-day focus, my new job also gets me involved in public relations, website design and intellectual property issues. I haven't quite figured out which parts I enjoy the most (definitely not intellectual property!), but you can bet that as soon as I do, I'll start volunteering for more of it.