Attendance as they walk in! A quick get to know you/math (counting and graphing) activity. Later in the year students can generate the questions and write them. Place on light colored paper, laminate, and questions can be added with white board marker.
How to set up the science center (with freebies) in your early childhood classroom. One of the BEST articles I've read on science centers both general and specific. Also provides fiction and nonfiction texts to pair with the centers.