There is a very good book, recently shared here on HN: Brain Rules for Baby, https://www.amazon.com/Brain-Rules-Baby-Raise-Smart/dp/09797... I recommend it. In short, the best things to develop toddler's intelligence are talking to them a lot, simple toys (boxes, plain blocks), and common tools for creativity like markers and paper.

I am also thinking about ways to develop abstract thinking in my baby. I plan to work on cards / minibooks to teach him some abstract concepts in a basic way: like transformations, combinations, logic, sets, etc.

I think it's very important not to force it on children, do not burden them with your expectations - they will rebel or build low self-esteem. It should be a delicate support, encouragement for them to follow their natural curiosity deeper, like Paul Graham described in his recent essay http://www.paulgraham.com/genius.html

I found some interesting views in this book http://www.amazon.com/Brain-Rules-Baby-Raise-Smart/dp/098326... - there is an associated website which might include some of the content. http://www.brainrules.net/. One interesting point the author makes is the importance of teaching children to identify non-verbal cues and cites studies showing that young children who are taught sign language (and are not hearing impaired) have a higher probability of success in later life. The following pdf could also give you some ideas http://www.dgmt.co.za/files/2013/05/More-than-Counting_web.p... - aimed specifically at math development between 0 and 5 years.