Probably, the reason you haven't received any answers to your question is that it's extremely difficult to answer. This is because so many factors are involved. We have student interns who do that sort of work for free, but we also hire freelance pro event photographers, pro web designers and graphic artists at rates of $50/hr or even more when we absolutely need to get something done right the first time, and in a limited period of time.
The pros have various overhead costs (eg, insurance, maintaining equipment and an office, etc.) that someone doing the work "for fun", "on the side", or just starting out simply don't have (eg, because they are using a computer that their parents bought them, etc.).
The rate you can get also depends dramatically on supply and demand in your area, a history of successfully completed jobs, your portfolio, whether or not you are willing to do a freebie for someone as a possible means of getting future paying work from them, etc.
If one had to pick a number out of thin air for a student with little previous professional (ie, paid) experience, but who can unambiguously demonstrate that they can clearly do the job, and if the employer isn't a university or non-profit, something like 2-3 times the minimum wage might be a good place to start.
Good luck.
Tom