Most of these activities are designed to do one of a number of things:
1) Help students see how Latin has contributed to English
2) Build their Latin and English vocabulary
3) Stimulate their interest in language patterns in general
I generally give these kinds of activities to junior students who finish their work early, or at the end of term when my students aren’t really in the mood for doing more substantial things. Mostly they only take 5-10 minutes to do, but they’re ready to go and require no preparation.
Here are a few examples:
harry-potter-spellscharacters.doc
romance-languages.doc (thanks to L Aronson for the idea behind this one)