There are so many things parents can do.
Read to your child. Make a routine of two or three times of day when you do this.
Go to the library to check out books. Ask the librarian for suggestions. Libraries usually have toddler reading groups, too.
Do your daily chores, but include your child while you do them. Measure flour. Stir batter. Rake leaves.
Play rhyming games with your son.
Engage your son in conversation. Studies show kids absorb more vocabulary and information when parents do.
If possible, try a weekly class for parents and kids, like Kindermusik, for socialization with other kids and the music.
Go to the playground to build gross motor skills and to visit with other kids (and moms).
Provide paper and crayons. At some point provide tape, scissors and glue sticks. Draw. Provide a box and other items. Build. Provide watercolors and paint. (My daughter's first painting experience was while visiting the Botanical Garden, and an adult there who was painting one of the flowers provided my girl paper and a brush so she could do the same. A great memory.)
Go for walks and take your time to see nature. Look under rocks for bugs. Collect leaves. Build snowmen. Notice the birds, and find a book to identify them.
Visit your local museums, parks, zoos, botanical gardens, pumpkin patches, farms. Don't expect to stay long or see these places as an adult would. Bring crayons and paper to copy works of art on display or draw favorite animals at the zoo.
Find some good CDs and dance.
I've found a spot on a wall and have made floor to ceiling murals out of construction paper with my daughter as a decoration / project.
Get a book on science experiments and do the ones geared toward your son's age.
Get letters for the bathtub and the fridge.
Label items in your home with signs so your son sees the name of the item.
Enjoy!