The first activity, one which I use as an ESL teacher, has to do with flash cards.
Don't know where to find good flash cards? Try googling 'ESL flashcards'. There are many different sites - most of them are free.
One site that I have used before is: eslflashcards.com
This website has many flashcards that cover a wide range of basic simple nouns, verbs and adjectives.
Print the flash cards twice - so you have two sets.
With two sets of flash cards you can play a wide variety of games using different lanugage structures.
One on one - the student can play a memory game.
With a partner the student can play "Snap" or my personal favourite "Go Fish".
I like "Go Fish" because you can adapt it to suit a different language structure and it has a question and answer element. For example, with flash cards for different places I have the students ask: "Are you at the .......?"
If the other person has the cards they say "Yes, I am at the ......", but if they don't have the card they say "No, I am not at the ....."
You can also use one set of the flash cards with another game like Jenga or Connect 4. To have a turn of the game the person with the flash card asks a question. For example with the verb flash cards the person might say "What are you doing?"
and to have a turn of the game the student must look at the card and say "I am ....."
You could do the same with sight words, read the sight word to have a turn, or with any flash card.
Once you have shown the student and another student how to play the game, you can just send them to play the game with a partner. As they master the set of flash cards, you can replace the set with a different set of vocabulary. It is a great game for non-ESL students to play with ESL students because it is easy and the non-ESL students provide a good language model for the ESL students. It could be a great idea for fast finishers to do.