I always start the year talking about safety. One of my first right hand assignments is a safety poster. This past year I also had students make safety posters for the classroom. They turned out great and stayed up the whole year (you can never go wrong with safety posters in the classroom :)
I like student work much better then store bought posters and whenever I am observed one of the expectations is that we have student work posted. Having these posters up serves as both a reminder to "be safe" and as a check off on my teacher observation forms.
Don't have room? See if you can hang them from the ceiling. Use a large sheet of construction paper and glue one child's poster on one side and another child's on the other....that way if they start to "spin" you always have a safety poster showing. You can also tape them on cabinets or use them as a boarder high up on the wall (just have students write/draw big so that it can be read from ground level).
The funniest poster this year (and remember I teach fourth grade) was a No Drinking in the Lab poster where the child featured a Miller Light beer bottle. It had me laughing so hard that it was featured in the center of all my posters.