Reddit reviews 3,000 Solved Problems In Chemistry (Schaum's Outlines)

Crash Course has a fun set of videos for each of the topics typically covered in a gen chem class. They're not super in-depth, but they'll serve as quick refreshers for the basics.

In addition to /r/chemicalreactiongifs I would recommend Periodic Videos.They also have lots of fun demos, but with more discussion and fun anecdotes.

If you're looking to hone your chemical instincts, I would actually recommend an older book called "Voyages in Conceptual Chemistry" by Dan Barouch. It's a source book of chemistry problems, but with a greater focus on concepts and critical thinking. Few (if any) of them require explicit calculations, which makes them great for class discussion. The problems still involve relevant equations, but with a focus on the relationships between and proportionality of variables in equations. Each problem even has 3 associated hints to help guide discussion and students' thought process.

To give you a sense of the kinds of questions in the book, here's an example of a fun but tough stoichiometry problem without calculations:
"Your project is to determine the molecular formula of an unknown hydrocarbon (a compound consisting only of hydrogen and carbon). It is burned completely under tightly controlled laboratory conditions and the only source of oxygen is a balloon inflated with pure oxygen gas, attached through an inlet valve to the combustion chamber. A friend pulls you aside and whispers in your ear that the number of molecules in the hydrocarbon sample is the same as the number of oxygen molecules in the balloon. Keeping this tip in mind, you perform the combustion reaction and watch the balloon shrink. When the balloon is completely deflated, the combustion reaction stops, and you notice that four-fifths of the hydrocarbon remain.
What are the two possibilities for the molecular formula of the hydrocarbon? Assume that the reaction went to completion and there were no side reactions or by-products.

Hint 1: What is the general reaction for the combustion of a hydrocarbon?
Hint 2: What is the limiting reagent? What's the stoichiometry of the reagents in the reaction?
Hint 3: From this information, what must be the stoichiometry of the products?"

This is possibly too difficult for an introductory chemistry class, since they won't realize that C3H8 is a reasonable molecular formula for a hydrocarbon, but CH16 is not. However, this should give you an idea of the caliber of the questions in the book.

For more traditional, calculation based questions, there are tons of source books out there. Schaum's has a pretty extensive one called 3000 Solved Problems in Chemistry

Finally, (but perhaps most importantly) check with the lead instructor for the course. Find out which topics will be covered and the relative difficulty of the problems that students will be expected to solve. Then choose problems based on those criteria. That way, you'll be certain that students are getting the practice they need.

One last tip, when you're working through problems in class, be sure to actually give students time to work on the problems themselves and encourage group discussion. There's a tendency to try to cram as many example problems as possible into a discussion session, but I find that this overloads students and pushes them towards rote learning. They just scramble to copy down the answers and figure they'll reread and understand them later. Fewer and more focused problems are more productive and lead to more transferrable knowledge/understanding.

Good luck next semester! Have fun!