This is a good place to start...

The best pancakes ever--heavenly hots! http://www.nytimes.com/2010/01/17/magazine/17food-t-001.html?ref=magazine

Well, I mean, short of many breads and chewy type doughs, you can just use it instead of AP flour in any recipe. If you specifically bought it for making muffins I'd guess you don't bake tons and tons, so just next time you make pancakes or a batch of choc chip cookies, use the cake flour. It's a slightly different (softer, finer crumb) texture but it would be fine.

These chocolate chip cookies that took over the internet like 4 years ago.

http://www.nytimes.com/2008/07/09/dining/091crex.html

Here's a really out of left field answer and forgive me if this seems totally wild and crazy!!

You could make a cake. The Cooks Illustrated cookbook (my new favorite cookbook) has a great recipe for both white cake and yellow cake. I made one for work and people kept asking me the brand of the box and I told them it was just a recipe and they then proceeded to call me a snob for not using a cake mix.

I do use cake mixes ... just not for making cakes.

My grandmother used this exact brand to make the best fried chicken in the world.

The same thing happened to me, and I started to use my cake flour in other recipes, as a substitute for all purpose flour. I am finding that it just makes the texture of things lighter - the other day I made a carrot loaf, which I've made many times with AP flour, with the cake flour and it was absolutely wonderful! I read somewhere though that because of the differences in gluten content you are supposed to substitute 1 cup plus 2 Tbs of cake flour for 1 cup of all purpose. Has anyone else heard that?

One of my favorite ways to figure out how to use up random ingredients is www.eatyourbooks.com - I've got all my cookbooks, personal recipes and favorite blogs added to my "bookshelf" on the website, and I can search to see which recipes have the ingredient cake flour - I pulled up about 450 recipes. I like this recipe in particular for using cake flour: http://smittenkitchen.com/blog/2008/02/29/big-crumb-coffee-cake/
(The website is free for limited use, and for the full version, you can often google to find a 3 month discount code - but I think it's totally worth $25/year.)

I actually prefer regular flour for most baked goods, but cake flour is pretty much required for an angel food cake.

Angel food cake! That's a great idea, and one I wholeheartedly second. So tasty, and really not so daunting...just incorporate your flour into the egg whites slowly! Use up the yolks by making some ice cream or pudding!

Tempura batter is what I mostly use if for.

Biscuits, biscuits, biscuits! They will be soooo light and fluffy. I also use it in my cream scones (which is essentially my biscuit recipe w/some more sugar).