Philip Neustrom has created Set your Instagram free!, a simple way to add Creative Commons licenses to your Instagram photos (something the service doesn't support natively, meaning that technically anyone who reposts your Instagrams risks a lawsuit). Wired has a good writeup by Nathan Hurst:
“What makes Flickr’s Creative Commons licensing so great is that it’s structured: You can search through their photos and just find ones that are CC-licensed and even drill down by tag, etc.,” says Neustrom. “So I wanted to provide something with the same level of structure.”
Users sign in with their Instagram accounts, choose the CC license they wish to use, and every photo they Instagram for the next three months (Neustrom included a re-up requirement so that users wouldn’t forget they’re sharing) will be CC-licensed. Take note, though: There’s no way to selectively license your Instagram photos — they’ll all appear on I Am CC. Whether you want them licensed in the first place is up to you, but chances are, they’re not making your any money anyway.