So, I'd say that the my two classes per week of the littlest ones in the school (1st graders) are definitely the trickiest ones as I am not very practiced at entertaining/teaching the cute, and rather rambunctious. 

Ideas? 

I do have a coloring template of animals from images from Google that seems to keep them entertained after we've talked about animals for a bit too long. 

I like to use starfall.com.  They have some great phonics worksheets that you can print off from their download center.  They can help you teach each alphabet letter and they include four pictures that start with that letter on the page.  Then I have the students clap or do some other physical movement if I say a word that starts with that letter.  My young students also like slap and memory flashcard games.

I worked with this age group last year. For part of each class we focused on four different letters of the alphabet. We would make flash cards and they would draw pictures on the cards of objects starting with each letter.

I did a few color lessons and those were good.  I would say "point to something green, point to something red"  and they enjoyed this activity.  Then I would pull an object out of a bag and they would identify the color. 

Sesame street is another good option.  The kids really enjoyed the clips where a new letter was introduced. 

Reviewing "what's your name/my name is" is another good idea.  Here's a link with a fun name song. http://genkienglish.net/namesong.htm

For my opening I would hide three simple items in a bag (three animals, fruits) describe and have them guess.  They loved it!

wow!  no co-teacher?  :o you are a trooper!  yeah, I've got about 25 per.  I call the two classes the "zoo" :)  they're super cute, but definitely a challenge.  Luckily I have pretty good discipline help from a non-English speaking co.  we usually make it through about 30 min, then I whip out some coloring.  Will try out these new song ideas though.

 I have about 20-24 little monsters (sweet monsters, but monsters none the less) and I don't have a co-teacher. i agree with all of the active lessons, they need to constantly be moving.       
One game I found that takes its time and really inforces the ABC's is the "racing game" that i what I know it as. If you have some space (we don't have much) make 2 or 3 groups, maybe color code them. they line up at one end of the class room, at the other end have 26 laminated abc flash cards (no lamination they will not live to see another class) call out a card, say a couple of words that start with the letter, and say go. the first students run and find the card and bring it back to thier team, then go back to the end of the line, and then do it again. It is really cute watching them look for the cards and yell at eachother.

any songs with clapping or movement are good.  practice the "m" sound for a bit, then have the students write "M" in the air with their fingers.  (teacher will model it mirrored).  Then you can say some words like "Monkey.  Banana.  Tree.  Make."  And have them stand up if they hear the M sound.  Or even play a children's song and have them stand up or clap whenever they hear a specific word or letter sound. 

Since their level is so low, the best way to communicate is to use pictures.  incorporate some pictures they know and some they dont, then practice the words with flashcards and/or PPT.  Once they get comfortable with the words, there are lots of games you can play with the flashcards or PPT.  Have them guess what T is drawing, or find the flashcard of the word you say, or whatever. 

Also, when I want to get my first graders to focus, I will clap twice and chant two letters of the alphabet.  Then they have to clap twice and chant the next two letters.  At first it was difficult for them but they are getting good at it now.  Baby steps ^ ^  Hope this helps