Here's a link too: http://www.countrycalendar.com/Country_Store/hats/hat_sizes.htm
Remember, cheap isn't always better. If it's a felt hat, the cheap ones are shitty and cheesy; a good one will run you over $100 (or plus, depending how good you want).
Straw is stiff; I love palm hats, they are flexible (my kids wear them, and they pop back into shape easily) and they can be new for under $50--this one is my favorite, called the Caroline Too:
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It sits lower on my head, which I like, and it was about $47.
It's made by Atwood http://www.atwoodhats.com/index-2.html
And it's the same with boots; buy a good, solid pair and and they will last forever, as well as being comfy (I don't really care about the fashion thing--in fact, fashion boots, like Lucchese, really bug me)--Ariat and Justin are good brands, and Double H is affordable and still nice. Watch out for slick soles--great for riding, not so much for general wear--and keep your heels lower if they're going to be for all-around use too.
This is the pair I have--Justin Tekno-Crepe, which are kind of all purpose,and ran me about $160: