We have been using a few products from The Critical Thinking Company in our homeschool this year. I let the kids choose their own from the catalog, as long as I could buy it as a PDF. I much prefer printing these myself and having the file on hand for siblings to use, too. I just print out a bunch at at time and paper-clip them together for the kids to grab when they are scheduled to do logic.
Grace chose "Think-a-Grams". She probably does about 10 of these a week and they have been a good mix of easy, challenging, and nearly impossible for her to figure out. I encourage her to set aside any she can't figure out, and we have found that in most cases the answer will come to her a few days later.
A few examples (and their solutions) from Think-a-Grams B1 (recommended for 7th-8th grade)....
|Solution: "Order in Advance"|
|Solution: "Center of Attention"|
These puzzles look easy enough when you know the answer, but most are quite challenging until you "see" the solution. My boys are using Dr. Funster, also from The Critical Thinking Company. I will do a little post on that soon.