Trains..............
My house is a huge train set. every one buys them for my DS 2.5 He has every Thomas Toy that Target sells....
Also I have recently found a new store in my area that sells Thomas toys the wooden ones and it is called A C Moores. Their prices are comparable with the other train shops, only they offer 50 % of cupons and will take competitors price off cupons. So you can get a train set for only $20 instead of $40..
Also on a recent road trip we have found the Kid K'nex. They are wonderful. They are a bigger version of the big kid ones. They can come in a 'jar' and you use the top of the jar as your base and build off of it from there. There are cars, trucks, fire engines..
My train finatic actually said he'd like a big set one day. They range in price from about $4- $20 and come in their own carrying case..
In fact we decided to get him one and have it be the gift from his new sibling when he comes to the hospital to visit. I thought it would keep him entertained, but he would remeber that his 'baby' gave it to him..
HTH