We’ve enjoyed unit studies focused on literature or topics in science, nature or history. They’ve lasted anywhere from a week to a school year. Sometimes we put aside everything else and focus on the unit study, other times we complete core work first and then dive in.
I try not to reinvent the wheel and often start with resources from Homeschool Share, but also can’t usually leave well enough alone and tend to pull together lots of resources. Utilizing the internet and a library this can be a mostly free way to pack in a lot of learning while having a lot of fun!