Shortly after reading about "Circle Time" over at Preschoolers and Peace, we incorporated it into our school day. It is the first "school" we do after breakfast, and everyone loves coming together for some learning on the fun side. Anyone that is not napping (usually age 2 and up) participates. And I continue to be amazed at how much the young ones learn!
Currently we are learning the States and Capitals and reading the poetry assignment from Sonlight Core 2.
In the past we've used Circle Time to do our Character Study, learn praise music sign language, watch Proverbs DVD, and in the summer: School House Rock!