GPA questions are tough. There's no guarantee when it comes to graduate school admissions. While some graduate programs apply cutoff GPA scores in order to weed out applicants, this is not always the case. We can make predictions, but there are many factors at play - even factors that have nothing to do with you can influence the availability of slots in a given program and your chances of getting in.
Now, remember that graduate programs look at your overall application. Grade point average (GPA) is one part of that application. Several other factors, outlined below, are also important components of the graduate application.
Graduate Record Exam (GRE)
Grade point average tells the committee what you did in college. Scores on the Graduate Record Exam (GRE) are important because the GRE measures an applicant's aptitude for graduate study. Academic performance in college often does not predict academic achievement in grad school, so admissions committees look to GRE scores as a primary indicator of applicants' capacities for graduate study.
Admissions essays are another important part of the package that can make up for a low GPA. If you address the topic and express yourself well it can allay concerns that arise because of your GPA. Your essay may also offer you the opportunity to provide context for your GPA. For example, if extenuating circumstances harmed your academic performance during one semester. Beware of griping about your GPA or attempting to explain four years of poor performance. Keep all explanations concise and don't draw attention away from the central point of your essay.
Recommendation letters are critical to your admissions package. These letters demonstrate that faculty are behind you - that they view you as "grad school material" and support your academic plans. Stellar letters can trump a less-than-stellar GPA. Take the time to nurture relationships with faculty; do research with them. Seek their input on your academic plans.
Not all 4.0 GPAs are equal. The value placed on GPA depends on what courses you've taken. If you take challenging courses, then a lower GPA can be tolerated; a high GPA based on easy courses is worth less than a good GPA based on challenging courses. In addition, some admissions committees compute a GPA for major coursework to assess a candidate's performance in the courses that are deemed essential to the field.
All in all, if you have a solid application package - good GRE scores, an excellent admissions essay, and informative and supportive letters -- you can offset the effects of a less-than-stellar GPA. That said, be cautious. Carefully select schools to which to apply. Also, choose safety schools. Consider delaying your application to work hard to increase your GPA (especially if you don't gain admission this time around). If you're looking at doctoral programs also consider applying to master's programs (with the intention of possibly transferring to a doctoral program).