Games are great fun. And many a game gets played whilst on holiday. All great for Stimulating the Mind.
Subjects, Racing Patients and 500 were hot favourites with my family while I was growing up. 
How Do You To Play These:
Subjects:
1. Everyone gets a piece of paper and a pen/pencil. 
2. Then they write list of topics like:
Boys Name
Girls Name
Country
Song
Movie etc
...until you have a good sized list.
3. Then someone picks a letter. They open up a book, open up a page, they turn away and then place finger on a word.The letter their finger covering is the chosen letter.
4. Then you have to write down a word related to the topic starting with that letter.
5. After a certain time everyone stops writing and the list is marked.
Each topic is read out and everyone says what they have. If someone else has your word then this is crossed off. You get a mark for each unique word.
6.The winner is the person with the highest score.

Racing Patients:
This is a card game.
1. Everyone gets a pack of cards.
2. Someone yells out "Go"
3. Everyone puts a pile of 13 cards to one side and turns the top card over. And then they place 4 cards next to this pile face up.
4. You build up Ace to King in each suit, in the middle of the table.
To do this each player :
~ places Aces out first on the table, then 2,3,4,5 etc.
~ builds cards down from the 4 separate cards in numerical order of numbers going down eg 9,8,7,6 etc and it must be built red suit, black suit etcor black,red etc.
~ turns over 3 cards at a time from the remaining cards in their hands and plays the shown card out to the middle or onto the cards faceup on the table.
~ fills up any gaps from the faceup cards with either a card from the set of 13 cards or from the remaining cards in their hands.
5. When the first person gets rid of all their pile of 13 cards, the game is over.
6. Everyone else then counts up how many cards they have left in their pile of 13 and double it.
7. The cards are sorted out in the middle of the table. 
8. Everyone then subtracts the number they got from 6. and counts any remaining cards. This is their score.The winner of course does not have any to subtract out.
9. The score is written down and it could be a negative number.
You play as many rounds as you like and add up the score of allthe rounds for the overall winner.

500
This is a card game,with  instructions too long to put here.
But it is a great game for 2 to 6 players. The most common version being for 4 players.  
For more games Watch Out For  Stimulate The Mind With Games Part 2