I've bought a few things...
Miquon Orange
Handwriting Without Tears K
Building Foundations of Scientific Understanding
So far we've been using the library's copy of OPG, but I'll probably end up ordering it soon.
I'm using Salsa with my preschooler (3.5), along with Spanish music and children's books from the library. She really enjoys it and is picking up quite a bit.
I'm basically using P3/4 as a list of book suggestions. I request the ones that look interesting (and secular) from the library, using ILL if necessary. We've really enjoyed everything we've read so far.
My dd (3.5) is subscribed to Click, Ladybug, High Five, and Your Big Backyard. All were gifts from family members. She loves her magazines, and we read them over and over again.