I found this link about making citrus vinegar by simply taking your leftover citrus rinds, putting them into a glass jar, and filling it up with white vinegar. In this jar is some de-zested lemon peels, and some grapefruit peels. My jar isn't quite full here.
Wait till the vinegar starts to smell like citrus, and pour out! Talk about easy! And getting the most out of your purchases!
I used it for adding to my wash machine for my diapers. I think it helped, but it's been hard to tell since we have an HE wash machine, and I've been battling with it to get my cloth diapers fully clean. But that's a post for another day!
Or the author of the site, Crest Cottage Creations, suggests diluting this citrus vinegar half and half with water, and putting it in a spray bottle to use with baking soda for cleaning. She says it's an excellent degreaser. If you haven't tried using vinegar and baking soda to clean with, I highly recommend it!