Some people swear by Sudoku as a memory and mentality strengthening activity. The learning curve is moderately steep, but once you get the idea, you may find you are looking for challenging Sudoku puzzles.
The Toronto Star has a link to their Sudoku puzzles. They also have an explanation as to how to play the game, along with solutions to the puzzles:
A REBUS is a puzzle using words and numbers, sometimes called a pictogram puzzle. Rebus puzzles use pictures, symbols, and letters to represent a word or words. These are really great for kids or adults because you have to use both sides of your brain. Click on one of the REBUS #s below: