Free exploration is my favorite kind of play. However, as a public school kindergarten teacher, I've got to work the academics into that free play. Lately I've been putting a new invitation on the light table every week. Here are my first three. The pictures show up better when the light table is not on.
Invitation to make letters using round rocks, markers, or dots. Source for these great templates: http://playathomemom3.blogspot.com/2012/06/letternumber-templates.html
Invitation to count. Clear cups with numbers. Small round translucent rocks for counting.
Invitation to match uppercase and lowercase letters. The templates were made on Word and printed on regular transparencies. The letters are simple small foam letters.
The light table on. The letters all matched! The camera makes the bulbs stand out. In reality, the light is very diffused.