Seriously....a week? I do not see where anything is stated that there is consistently from year to year a set time to honor principals.
During the teacher appreciation week, all other members in the school share in the treats, luncheon, etc. I do not think that anything else is necessary.

Here's some ideas

Monday- A note or thank you card
Tuesday-A treat or snack
I can't think of anything at the moment but that's to get started

Principal appreciation should be included in your staff appreciation luncheon or however you celebrate the staff. He is a staff member too and if you single him out what are you saying to the rest of the staff.

There are other ways to get the principal "on your side".

Virginia's governor declared a week last winter Principals' Appreciation Week. It seems to be Virginia's week alone.

thank you for your reply...that is a good idea to include all staff...I looked into it further and I think offical principal aprreciation days are a state thing. We had a week in January declared principal appreciation week for 2009..cannot find any info for 2010 though

We do "staff appreciation" during teacher appreciation week. Everyone on campus, from the janitors to the principal gets goodies. I had never heard of the other.