Enchanted Learning k-3 theme
http://www.enchantedlearning.com/themes/
Pre-K themes
http://prekinders.com/theme/
Preschool Themes - 170 Early Childhood Education Themes
http://www.everythingpreschool.com/themes/index.htm
month by month themes
http://littlegiraffes.com/teaching-ideas/themes/
Thematic Cross-Curricular Units
http://themes.atozteacherstuff.com/