We don't buy for many:
My parents
Inlaws (last year they gave us a gift! Too bad the card was made out to my husband and his ex!)
Daughter
Son (new this year)
Niece
One of husbands cousin's kids (the only one still under 18)
We don't exchange with either of our brothers and we don't do for my niece or nephews either. Our gifts to each other is NOT having to buy gifts for each other! I found when I had a kid, people were VERY happy to agree to no gifts!
In the four and a half years I've been here, I have sent gifts to my brother and sister-in-law
once (and they complained about what I sent!), and a gift to my sister once (who was so touched by what I sent that she cried... I can't top that!).
My husband is very good about sending flowers, wine, and chocolates to his stepmother and his grandparents. And he'll usually pick out some oddly fascinating gadget or an interesting book for his dad.
My husband and I officially only give gifts to each other on our respective birthdays, but I paint these terrible little watercolour cards for special occasions (his birthday, anniversary, Christmas/New Year's combined, and Valentine's Day). I mean, some of them are cute. But they're not exactly technically well done. And one year, I wanted to make a thing (a Domo plush, made from a brown towel and some felt), so I told him it was his Christmas present--he loves it.