Happy St. Patrick's Day!!! Here are some of the projects I've done with my children to help celebrate and decorate our room for St. Patrick's Day. 
The first picture, you can see is very simple.  There are actually two different shamrocks hung on the wall.  The giant shamrock was done by allowing the children to free paint a big piece of butcher paper (the big roll paper) and then cutting out a shamrock.  Luckily, I have an artist that works in my classroom, however, before she started working in our classroom, we would make an overhead sheet using sharpies and ziploc bag and blew it up on the wall using the overhead projectors.  Then they decorated the two little shamrocks.  The one they did by free painting with textured paint brushes.  The second was done by gluing green sand to decorate the shamrock.  I like using sand and other textures with my two year old children because I think it makes their projects more interesting to them.
The second picture was free painted rainbows the children did.  This was obviously very simple - they just used the colors of the rainbow to make their own. 
The third picture, is an idea for a bulletin board.  I got this idea from a previous lead teacher.  I think it is adorable.  Last year when our classroom used this bulletin board idea, we used "Let Your True Colors Shine Through" for the caption.  As you will see when you scroll down, I used this for a project.  All we did was trace the children's hands on one piece of construction paper and then stapled the other colors of the rainbow to the back and cut them out!
This fourth picture is a new project for me and I loved it!  For St. Patrick's Day, I love when teachers for younger children do a project that shows blue plus yellow equals green.  I decided to spice it up a little bit by working in this name exercise.  I used masking or painter's tape (preferably painter's tape) and taped their names to the construction paper.   I put yellow and blue finer paint on the paper and let them smear it around, then once it dried, simply removed the tape.  I like it because it has a rough graffiti type look.
Last but not least is a project idea I got from pintrest.  As you can probably see, we painted their hand and each color the different colors of the rainbow and then finished the rainbow.  This is very easy but very cute!

I totally recommend pintrest to any teachers, they have great ideas for teachers!!