Not knowing your son's learning style I am going to give you some DVD's and websites that you may want to check out.
Leap frog has great videos:
"The Letter Factory" (teaches letter sounds)
"The Talking Words Factory" (pre-reading)
"Talking Words Factory 2: Code Word Caper" (reading)
"Learn to Read" (ready for school skills - reading, punctuation, story comprehension)
These videos still keep my oldest engaged and he is an advanced reader.
Websites (all free, but you may have to register w/ minimal information)
www.literactive.com (they have a section for ESL)
www.kidport.com (ESL section as well)
www.starfall.com
http://www.storyplace.org/preschool/preschool.asp?themeid=21
http://resources.kaboose.com/games/read1.html
I hope these help. Let me know if you need more resources. I home school, so I'm always looking for alternatives on the internet to supplement what we do in class.