Am I being taken advantage of by working on a committee member's research with no payoff? I am currently pursuing a Master's degree in Computer Science which requires me to have three members on my graduate committee. 

Last August one of the committee members asked me to work on a project for him as part of my graduate work. However, the work was not enough for a thesis, I would need to switch from thesis-track to project-track, which I am not interested in doing, and the topic wasn't what I would like to work on full-time for my research. 

My major professor suggested I work on the project for a shot at getting a publication under my belt for the work I will have done. Because of this I accepted the proposal and put a ton of time into the project on top of my research and course load. Recently, the research was funded and a poster was made to present the research. Lo and behold, I was not listed as an author on the poster with the professors despite my countless hours slaving away.

There have been no publications yet, so I don't know if I will be listed as an author on the actual paper but, being new to this, I would like to be sure I'm not being taken advantage of. I've got enough things to take care of outside of the project and was expecting some sort of payoff if the research had gotten this far. 

Don't get me wrong, I'm thankful for the opportunity. I'm still assisting with the research and would like to continue to assist the professor with hopes of at least getting a good letter of recommendation for a PhD program but, if the general opinion is I'm being taken advantage of I would like to know to perhaps confront the faculty member.
Yes, you should discuss the issue of authorship. From this description, we can't tell you whether or not you are being taken advantage of. In general, whether authorship is appropriate depends on the intellectual content of your contribution. 

To discuss the issue, start by saying "I'd like to discuss the issue of authorship on this project." If you'd like to be direct, you could then say, "I have committed a lot of time to this project. I am under the impression that my work is substantial enough that I might qualify as an author on papers arising out of this project. Under what circumstances would you consider including me as an author?" 

If you'd like to be less direct, you could instead ask several questions about your committee members' philosophy on authorship. "What sort of contributions do you believe qualify for authorship on a project like the one we are working on together?" 

If you don't like the answer (the person refuses to make you an author), then you need to set some boundaries in a professional manner. "I'd like to continue to contribute to this project. However, since there is not a possibility of authorship here, I am sure that you understand I need to prioritize my other work. Going forward, I can commit to X. If you need more help than this, I think we should revisit ways I could be compensated or qualify as an author."