Junior (my 4 year old) is obsessed with construction. He is forever making things and then cluttering up the top of the piano with his current favourites. It has got to the stage that each evening we have a purge and he has to choose one favourite construction to leave out and the rest get packed away.
He has always loved his Lego Duplo but this year he has moved on to the real thing and is constantly getting out the box of small Lego blocks and making something new or altering a work in progress.
He is also very keen on box construction. This is very environmentally friendly as he is constantly raiding the recycling bin for the right piece to add to his masterpiece. I'm forever returning the constructions to the recycle bin but he loves it and it only costs me a bit of tape. Well actually a lot of tape but you can't stem his creative urge. After weeks of his frustration wresting with a role of sticky tape, I lashed out and bought a large, heavy based tape dispenser. It is large enough to hold a thin roll of sticky tape and masking tape and Junior is so happy with it.
Another long term favourite is his box of Liquid Crayon markers. They are a bit pricey but his Aunt (a year one teacher) put us on to them and they really are great. They have given him hours and hours of entertainment and are still going strong.