I have a great system with my friend--we pass stuff back and forth. Luckily, our kids are spaced right that we can do this well--she has 5 kids, I have #4 on the way. It seems more special, coming from her kids, rather than a "straight" hand-me-down! I also shop second hand quite a bit, and my favorite for winter things is the LL Bean factory outlet by my MIL's (we go for Thanksgiving, Black Friday it's 30% off the entire store!).
Right now my older two (DD10, DS8) are EXACTLY the same height and weight, so there's no "sharing" between them. DD10 is developing her own tastes, so I try to keep her brands and styles in mind when I shop. DS8 would go naked--I find he's very tough on pants (what boy isn't?), so I always look for those when I shop. For us, it's less an issue of money as value, and wanting to have money for other things.