Everything Has a "Home"
(British Columbia, Canada)
My 6-year-old son was the only boy amongst 4 sisters until our newest baby boy was born a few months ago. He has been a little spoiled as the only boy his Daddy had to buy boys' toys for.
He has tons of little play sets, cars, dinosaurs, etc. As we don't have a lot of extra money, I've had to work with what we've got or been given for organizing his toys.
We have a great plastic drawers set, with about 9 drawers in it. I organized it so that each drawer stores toys by theme (e.g. dinosaurs, superheroes, monster trucks, "Car movie toys", etc.). These are really great, as the drawers come in different sizes, and you can buy more and stack them on top of each other.
We were also given a low bookshelf that has made for excellent toy storage/display. His matchbox cars and Speed Racer car sets are each kept in little backpacks on this shelf.
The more complex sets with small or breakable parts, such as racetracks and train tracks, are kept in the original boxes up high on shelves in his closet. We get them down by special request, and they are cleaned up and packed away immediately when he's finished playing.
The most important aspect to keeping his toys organized has been teaching our son that everything has a "home", and training him to put each toy away where it belongs!