I play Brain Trainer on DS every day and I'm getting better at Sudoku. i wouldn't touch it with a barge pole before all this but I made myself do it and now enjoy it.

Lumosity do some fun free games on trial. Just keep making free hotmail or yahoo internet accounts and you can sign up for a free fortnight each time.
The memory puzzles really show me how bad i've become. I have the attention span of a chicken.