This is a fun question, especially since I love to shop and bring back gifts from wherever I've been! Sometimes, tho, I find myself spending too much time shopping for gifts because I like to look around and find things that I think each person will really like.
My kids will usually shop for a few close friends, but they've never brought back gifts for an entire classroom. They have, however, from time to time brought back something for a favorite teacher. When my youngest daughter was in fifth grade, she had a teacher she absolutely adored. When we took a vacation to Disney that year, my daughter wanted to bring something back for her. One evening we were sitting in a restaurant somewhere on International Drive, (Pointe Orlando, I think), and my daughter looked out the window and spotted two life-size cow statues, dressed in touristy outfits. They were posed in front of an ice cream parlor. My daughter knew that her teacher loved anything to do with cows, (she had them all over the classroom), so after we ate we went over to the cows and I took a few photos of my daughter posing with the cows. When we returned home, I developed the photos and had them enlarged and put them in a frame for my daughter to take to school. My daughter also wrote a funny saying by each cow, something that the teacher was always saying to the class. She couldn't wait to take it to school and give it to her teacher, and was very pleased when the teacher hung it up by her desk. I thought it made a good gift because it was made specifically for that teacher and it was very inexpensive.
There is also a place in Epcot where you can make weird pictures, (your head on a cat's body, etc.), and e-mail the result to wherever you like. A few times my kids have e-mailed crazy pictures to their classrooms, along with a short message. I know these have always been well received, and they cost nothing to make!
Another time, after a trip to Discovery Cove, my daughter did a whole project on dolphins and she couldn't wait to take in the photos of herself swimming and interacting with a dolphin.
On the teacher side of things, I've had several students bring back gifts. One time a student presented me with a huge bag of oranges, and I remember one time receiving a cute little alligator figurine, (I have a thing for gators and I guess this student picked up on that!), and once a student brought back a tiny cactus plant from his trip out west.
So, to wrap up this long post, I think it's nice for the kids to shop for a few small gifts for special people in their lives, and as a teacher, I love it when a student returns from a vacation and shares a few photos and experiences from his/her trip. It becomes a learning experience for everyone.