This is the first time I've posted anything I've made. These three shirts were made from things I bought at resale shops. The yoked ones are from an XL men's shirt combined with a dress shirt (inspired by many a post here) and the blue one was made from a large button down. The green and white yoked shirt was my practice so its a little shaky. Also, please excuse the crappy pictures and un-ironed material. Any comments are greatly appreciated!!
Thanks for looking!
Before:

After:










Tutorial Added:
OK, please excuse the terrible paint tutorial. I think I can explain it better in words than the pictures.
You'll need a shirt with those long things on the collar that you tie in a bow. I think another kind would work though, as long as you have a strip to put in the middle. Make sure the shirt is too big for you so there's enough fabric to gather on the bottom.
Step 1: cut off the collar things, leaving about half an inch on the still-attached part so that you can fold it in and have a clean edge (sorry if that doesnt make sense...) Sew along that folded edge, and if the collar is wide enough, fold it in half length wise and sew to make a maderin collar.
Step2: Cut along all of the red dotted lines in the picture
Step 3: Sew one of the collar bands onto the bottom of the top half of the shirt.
Step 4: Sew the bottom of the shirt onto the bottom of the band, gathering the material as you go.
Step5: Re-attach sleaves at whatever length you want
Step 6: Sew edges of shirt along red dotted lines in order to fit as you like.

Alright, I hope that was clear! feel free to ask any questions!