I'll second the take apart Battat toys - I think we had a different brand, but same concept.
Duplos are great if he doesn't have those yet. And you can never have enough Duplos/Legos. My eldest was in a day care that has one big room for infants 6 weeks old to kids 3 years old. At 10 months, she started taking apart Duplo creations, leaving a number of 2 year olds very upset. Fortunately, she learned to put them together at 12 months. Later, we bought some old large Lego collections that we found on Craigslist or Ebay. My girls (16, 14 & 7) still build stuff while they watch movies.
My middle one was really into the Fisher Price Little People toys, but my eldest had no interest. I'd test those out at a friend's house before buying those.
