I just registered on the forums, actually because I read a few other people have the same problem I had two days ago. I already wrote a topic about this on the Steam forums, but it seems to be (obviously) more active here, and I just read a thread from somebody with the exact same problem with no solutions mentioned. So I thought why not post it here too.
I only know that this works with W7 and the Steam version of Super Meat Boy. So definitely try it out, and if you got it to work under different circumstances let me know so I can put it here.
Are you like me? Did you uninstall Steam without knowing it uninstalls all of your games? Did you want to hang yourself after finding out your Super Meat Boy save was gone? Then worry no more, because we can get your save file back (using W7 don't know about other OSes).
Step 1. Try to find your "Steam/steamapps/common/super meat boy/User Data" folder. If it's still there go to Step 7 if not go to Step 2.
Step 2. Install Steam (do not download any games).
Step 3. Do a System Recovery that goes back to before you uninstalled Steam/Super Meat Boy.
Step 4. Download Super Meat Boy from your games list.
Step 5. Open Super Meat Boy and then close it again (to create new User Data folder)
Step 6. Go to "Steam/steamapps/common/super meat boy/" folder.
Step 7. Right click the newly created User Data and choose "restore previous versions".
Step 8. Look at the dates of the previous versions, but MOST importantly look at the times. The best would be to find one under the date on which you deleted Steam/SMB but at a very early time before you committed the sin. Copy the relevant folder.
Step 9. Replace the newly created User Data folder with the one you copied.
I really hope to save a couple of lives this way.