I am an author on a poster, but I am unsure of what to put for my affiliation. I am a graduate student, but the poster and corresponding project is in no way connected with my university. I work for another university and the project relates to materials from that university, however they are not sponsoring the project. Any suggestions?
Traditionally, affiliation address must be where the research has been conducted therein (this is the statement given by some scholarly journals in Guide for Authors).
Professors normally use their official affiliation for any publication/presentation even if their university has not supported that research. Probably, because their secured salaries let them to work on an external project. This is different for graduate students, but still can be applied.
In any case, nothing stops you for using both affiliations in your poster. Normally, a graduate student is gaining credit from his/her affiliation. Then, two affiliations can be indicative of your research potential, as you have not stuck to your academic project.