Challenge your brain. Some cognitive decline, such as in memory and thinking skills, is a normal part of ageing. Studies have shown that a lifestyle that includes cognitive stimulation through active learning slows this cognitive decline. Do something good and stimulating for your brain like assembling a puzzle, learning a foreign language or learning to play a musical instrument.
Jigsaw puzzles are fun in a slow and easy way, crosswords & find-a-words are challenging. Building blocks can also help your memory and your hand-eye co-ordination.
Now I know that money is an issue for many people, myself included so I decided to see what I could find cheap or free online.
Do a search for crosswords online and you will find a whole bunch of crosswords from Newspaper sites, some are free some are not. I avoid newspapers as much as possible so you will need to check them out for yourself.
Arkadium has dozens of word games on their site and I highly recommend it.