Ha, you guys think the market is over saturated with people with a B.S.? Try being a Ph.D. Nobody wants to hire a Ph.D. with little or no work experience when there is a glut of Ph.Ds with plenty of experience who can't find even a mediocre position right now. Sorry, grad school is not the answer. Grad school is only worthwhile if you are passionate about doing it. It is not a joke, and if the main reason you are going for a masters or doctorate is to beef up your resume, you will spend the next 3-10 years of your life suicidally stressed out and depressed.
I mean, you realize that a masters in the sciences will only slightly improve your chances of landing a position, and a Ph.D. entails at least 6 years of brutal lab work, student teaching, and living on a measly stipend, and THEN will require another 4 or more years of a post-doc (a position that typically pays ~$20,000/year) to even have a chance at being competitive. And that's only if you're smart/lucky enough to publish some groundbreaking papers (fat chance). And again, you'll have spent your best years living in poverty and toiling away in school, and come out in your 30's with little or no experience in industry and an even narrowed field of expertise. Many people complete a Ph.D only to find that there are only 1 or 2 positions in their field available in the whole country.
In my opinion, you're much better off spending that time searching for jobs and accruing real experience. Giog, do you really really want to work in your field, or do you just feel compelled to because you don't want your degree to be "wasted"? As I'm sure you realize, most lab jobs for people with a B.S. are quite low paying, with little room for advancement, and involve extremely repetitive, menial, and unrewarding tasks. In other words, you'll be a disposable employee doing bitch work.
Unless you have a deep-seated passion for whatever your degree is (I really don't know what a degree in "natural science" entails, is it like a survey degree for bio, chem, and physics?) I suggest you expand your idea of what kind of jobs you're qualified for. Maybe apply for business positions (sales, marketing, etc). A lot of recruiters in business are starting to realize that any moron can sleep through a business degree and would rather hire scientists or engineers for these positions. Are you interested at all in teaching? There is a demand for science teachers throughout the country. Do you like writing? Maybe look into scientific writing (those guys who write all those product manuals no one ever reads).
Don't just apply for lab tech jobs. Those are surprisingly hard to get nowadays (even though they suck and pay like $13/hour) because they are eaten up by people trying to get experience for grad school or med-school rejects.