Girl, read to him now! My son is now 3 and LOVES books. I have read to him since he was a teeny-tiny infant. We had three books: one was a soft one that said "I love Mom" "I Love Dad" "I love you" (three pages). One was a story about a dog and it had different textures/sounds and flaps. I held my son's hand and let him crinkle the crinkly pages and pet the dog's soft fur. He loved it. The third book I made myself (very easy). I got a little cheapo photo album and put babies and toddler's faces cut out from my parenting magazines in each photo slot. He LOVED this book. We'd look at the expressions on the faces. He would sometimes try to copy the facial expression of the child/baby. He would sometimes just stare at certain faces. I would explain how 'this baby is sad' and 'this baby is happy.' There was one girl he would always stare at a little longer than the others - an Indian little baby with dark skin and bright eyes. So if you make one, try putting a variety of faces in the photo album book.
As far as toys go, my son loved his teething rings, but his had a little rubbery-ness to it. I have since bought teethingbling.com bangle bracelets for a future child. They're the right texture I think. They're not filled with water or gel, and they're not hard plastic rings. I agree that toys that have a cause/effect would be great (kick it and it makes noise). My son loved his bouncy chair. He started on a Bumbo at 4 months too. I'd play with his stuffed animals with him too - making his toy dog sniff his neck and such.
Good luck. Start reading now! Have fun playing with him too. They grow up so fast - so enjoy this time. Take lots of pictures!