Is it gifts, writing off poetry or joining the teacher appreciation day? For me, it is not necessary to give some gifts or any stuff that you want, but joining the event is much better to recognize that they were important to us. What do you think?
If you are asking as a parent or someone with teachers still teaching, the best thing you can do it give her some of your time. Teach a class for her, on the day she has to compile the grades. Offer to cut out, laminate, or make copies. Print some color pictures if the school only has BW printers and you have a decent color printer - laminate or frame for the classroom (does she have a good picture of Obama and Biden yet?) . Donate books for her grade/subject either than your own kids are finished with, or that you have read and enjoyed (for MS/HS - make sure no bad words in them). At this time of year, you could always donate a pack of paper - white or colors. For elementary teachers, you can always collect and donate art/craft supplies. Make a batch of play dough (salt, flour, water, cook & cool).
You could also bring lunch for the teacher/s that day... or have it delivered. Something they never do in the cafeteria!
We live in a small town and I sent a letter to the editor of our local paper praising my son's teacher(s). Nothing beats public praise and it becomes something they can cut out and keep. I've also sent letters of appreciation to the school principal and superintendent and made sure to copy the teacher. Now I am a teacher and those notes really do mean a lot.