both my boys loved bricks. either the mega blocks or the early learning centre do a wooden blocks set which are both really good as they can bite on them as much as they want and wont brake. my son who is 3 in may still plays with his all the time now. only now he can use his imagination more and build things rather than just bang them or eat them.
As he is still so young,you should look for toys that are soft,brightly coloured(to stimulate his vision) musical......Mobiles are particularly good at this age,as baby can try to reach for thingsand this helps eye-hand co-ordination.He will be sitting up when he is around 6-months....and what he can play with may include soft cars,balls etc.