For the most part if you're just going to be looking for a job, they don't mean much, unless your minor is particularly applicable to the job your doing. For example, I have a friend who majored in communications, and got a minor in public relations (since there wasn't an actual major offered in public relations). Several of the jobs she sought were for PR
positions, and as such, this was of at least some benefit.
The only other time is in applying to graduate school if your major doesn't necessarily match up very well with the "typical" applicant. For example, I was a sociology major going to medical school. In order to show that I wasn't completely deficient in science, I picked up minor in Biological Sciences. By no means did this change my major from a possible liability into a strength, but was just a means to lessen the impact if someone thought sociology was weak.
Other than that, most minors don't really matter.