Yesterday I made a dress for my little girl out of an old dress of mine. I should have done a step by step tutorial, but I didn't (I was trying to hurry and make it during her nap time). If you have any questions, I'm happy to answer them though.
Here is the original dress. For a reference, it came down to my knees. Why did I cut it up and ruin it you ask? Honestly, it never fit well and the top was too wide.
Here is the dress I made for my daughter. It's a bit too long (remember she was down for a nap so I couldn't take measurements along the way), but I still like it. I have a bit more fabric left over that I think I'll make a matching headband with.