I have been put in charge for making a promotional poster/flyer for an event on my college campus. I'm not being paid, just volunteering and the event is a free event.
Is it okay to use fonts from dafont for this? I'm not sure if this counts as commercial use or not.

Yes, as it is not for personal/private use it counts as commercial use.
Just contact the author, explain your case and probably you may use the font for free or a symbolic fee.

Each author has his own definition of "commercial use". The best is to send this question to the author of the font you choice.

Yes. Correct. At the same time, worrying about a font to use on a flier is like worrying about the font you use for a publication. People use fonts all the time others have made in print everyday and in websites. However, contacting the author is always the safe bet. He or she will appreciate the gesture. If you are tired of downloading fonts and want to get to know how to become a graphic designer yourself, Learn iT!

You could always use a font designated as Free, in which case, permission for both personal and commercial use has already been granted, in advance.

~bito

I don't think it does count as commercial use as no one is making money from it. I would just go ahead a use any fonts that have a free for personal use license.