There are numerous ways to say thank you to a teacher. The most meaningful way to say thank you is to actually tell a teacher thank you! Sounds simple, but you'd be surprised at how few people actually say thank you!

Check out Disney's Teacher Hand Information for Teacher Appreciation

Another way is to recognize outstanding effort. There are numerous awards that you can nominate a teacher for. Again, it's something easy to do but few take the time to recognize that effort that great teachers put forth. I've included some links to some popular award programs specifically for teachers.

International Reading Association NEA Foundation American Stars of Teaching
The Teaching Award Wal-Mart Teacher of the Year Award ASCD Young Educator Award
National Teacher of the Year Time Warner Cable Teacher Awards Technology Excellence Award
National Education Awards National Kind Teacher Award National Social Studies Educator Award
History Teacher of the Year Awards History Educator Award VFW Teacher of the Year Award
National Teacher's Hall of Fame Rising Star Award Teachers Count Awards
RBC Tribute to Teachers USA Today All-Star Teacher Awards Cable's Leaders in Learning Awards
National Council for Geographic Education Award