Hiya,
We've just got back from a weekend away with our spirited 16 month old. You don't say how long your flights are, but ours were relatively short 1hr 15mins each way (we went partly in preparation for a long haul flight to America in May).
I bought Ben a new dinosaur book that roared, some linking rings, a mini Makka Pakka, and took lots of snacks and a couple of little favourite toys in his changing bag. Now, bear in mind that this was a short flight, but actually we didn't need any of them!!
The flight was short enough that just what was going on on the plane with the stewardesses and other passengers and all the new sights and sounds were enough to keep him occupied. He has a dummy which he had on take off and landing (helps with the pressure in their ears - something to suck helps that) - but I was actually very surprised at how calm my usually very wiggly boy was!!
I will be taking a whole arsenal of things for our 8 hour flight - but the plane will be much bigger so hopefully there will be at least a chance for a little walk up and down the plane.
Oh, he didn't have his own seat this time either and was sat on my DHs lap with an infant belt - he normally is not one for sitting on our laps for any length of time, but again the new sights, sounds and experiences kept him happy there.
How long are your flights?