I'm pretty new to Google Analytics, but I was surprised by how few UTM related projects there are on GitHub. Bossmode has already saved me a lot of time at my new gig, so hopefully you'll like it too. It works great on mobile too so you can take it with you! (There's also a native OSX .app thanks to MacGap)
Here's what it does:
- It constructs URLs with UTM tag strings.
- It shortens those URLs for easy sharing.