I recently decided to revamp Bug's toys and get rid of anything that doesn't fit into seven different categories...
2. Wooden building blocks
3. Matchbox/Hotwheels cars
4. Wooden train set (minimal Thomas expanded with comparable cheaper trains)
5. Animal figures (sturdy ones by Safari Ltd. and Schleich...I get them at Michaels or Joannes with coupons for 40-50% off occasionally, so I'm not spending the big bucks on these, but he'll eventually end up with a decent set)
6. Babies and stuffies (he's only got one baby doll but about 10-12 stuffies...and won't be getting any more!!) If I had a girl it'd probably be a few more dolls and a few less stuffies...but the amount is decent for now)
7. Pretend play...this is the biggest one, because it incorporates dress up clothes, play dishes and kitchen stuff, and some play workbench stuff...but I still keep it from getting out of hand.
Besides the stuff listed above, Bug has got a few hulahoops, a sand and water table, and a hand-me-down scooter outside...a kitchen drawer with stickers, paper, construction paper, gluesticks, safety scissors, crayons, colored pencils, and a coloring book...a shelf of books in my room and a small basket of books in the living room...plus a little "desk" in our home office with a handful of manipulatives on it.
We've got him a wooden train table off of Craigslist for $20 that he can use for just about every kind of imaginative play. If I were to find an inexpensive compact wooden play kitchen for him then we might add that to the mix. But really, with what he has everything fits in or on the train table and in containers on one side of the bottom of his closet.
I know we could be even more minimal than this...but this is what works for us right now. With a zoo membership, a museum membership, a library card, and access to both the neighborhood and several city parks...he's got a fairly well-rounded life without a ton of kid stuff overflowing every space in our house!!