Although Clergy Appreciation month is not an official part of the church year, it is just a good thing to do for your pastor! (Reminder, if you are from my church, you can ignore the rest of this post).
One thing that I have noticed growing up as a pastor's kid and serving on the ministerial health committee here in the South Wisconsin District is that congregations don't really need to do much for their pastors. All they need to do is give an occasional thank you, throw an occasional gift certificate, and invite the pastor out to lunch 1x a year. Simple and done.
However, what I would say is the key is the shower his wife (of course, if he is married) with love and care. Buy her gift certificates, give her pedicures, thank her for supporting her husband, call her and see how things are going, ask her if you can do anything, and ask about her life (not her husbands). The key to effective ministry is the pastor's wife! If you shower her, you will have a more effective, energetic, faithful pastor! Provide your pastor's wife this month with a gift and not just your pastor!