I found a couple of cool shops for brony clothes, so I figured I'd share them. Those of us interested in clothes like this end up searching for good clothes.
So, there's Shirts4Bronies: http://shirts4bronies.com/store/index.php?main_page=index&cPath=3
They have quite a few choices for shirts and hoodies. They're generally shirts and hoodies with pony pictures and designs on them.
And then, Corsair's Boutique has more than just MLP stuff. They have other things like Dr. Who and Avengers, pirate/steampunk, stuff like that.
Their Facebook page: https://www.facebook.com/corsairsboutique
Their Etsy store: http://www.etsy.com/shop/corsairsboutique
For MLP-related stuff, they have things like scarves, patches, a shirt, capelets, and cinch skirts.
Redbubble is my favorite because it's all created by indie artists.
I own This Pinkie Pie Shirt (http://www.redbubble.com/people/rozasupreme/works/8204295-paintie-pie?p=t-shirt) in black and This Vinyl Scratch Shirt (http://www.redbubble.com/people/hyperguy46/works/9153548-vinyl-scratch-drop-the-bass) in dark blue.
Great quality, only drawback is they aren't meant to be machine dried. Though I have accidentally dried them before with no issues.