JoAnn's is okay but honestly, I buy about 90% of my trims and buttons from an amazing fabric outlet just a couple blocks from my home. The owner goes to manufacturer's auctions and buys in bulk whatever they are getting rid of. The amount of unique and interesting trims is beyond anyone's expectations. See above pic. That's only 1/2 of 1 wall. There's about two more giant walls filled with literally thousands of buttons and trims. And most of these things are only 20-70 cents a yard.
Okay, now that I've made you all green with envy, I'll add that there are some amazing places on the internet that you can find just as amazing trims as long as you have the patience to wait a week (sometimes less) for it to come in the mail.
Here are some etsy sellers who offer some amazing trims (Note: I am in no way affiliated with any of these sellers)
If any of you have some great suggestions please include them in the linky party below!