Plan Toys, Ryan's Room, Educo/Hape, and Le Toy Van all pretty much have the same scale. It's just about 1:12 or 1/12. That means that for every foot in real life, you have an inch in the mini. As you can see in the photo above, the awesome mushroom bed (by Enchantmints) is smaller. Not much, but enough. In the play dollhouse, it's not going to make much difference. I'm sure my 2 year old is not going to mind. Pictured above is the double bed from Educo/Hape with the Plan Toys bunk bed and the Enchantmints bed.
And a little more information on other brands: Barbie and Blythe dolls (not the petites) are 1:6 scale. So there will be some stuff for them that you can use in a play dollhouse that will work fine because of the chunkiness of the wooden toys. I found some dishes in a box from when I was a kid that I'll be adding to the loot so she'll have some accessories.
For the rest of the play dollhouse posts, click here. They are all in one place.