I asked on twitter what other people do on the first day and got these replies...
from @JackieB: Have kids do "about me" sheet, hand out syllabus (without going over), get started on a "good problem" in groups (such as this) (I also like this problem that I have saved)
from @jreulbach: Do learning style survey (pages 18 - 23 ) and birth-order activity
from @MisterLemus: Changes yearly. Has given math attitude survey, introduce themselves by picking a fraction that describes themselves, frequency table of birth month, name tag activity (good for homeroom?)
from @ecmorrell: Complete get-to-know-you sheet, then teach lesson (in 90-minute block period)
Pretty good responses for a mid-Sunday afternoon query!
My evening update:
I had a few more responses this afternoon! Some great ideas...
from @Stelladuma: Give this problem to Algebra 1 and discuss strategies
from @AmberDCaldwell: This numbers "quiz" about the teacher
from @park_star: A math bingo review sheet; students work with other students to get answers to squares
from @jamierykse: A pop quiz (again, about teacher) - looks fun!