If you do not have backups, then you have just learned how important regular backups are! You have also learned that it is always good to inspect scripts you "download" from the Internet.
So, turn your computer off NOW. Get a liveCD with linux onto a USB dongle, plug in a USB hard drive or use a second internal hard drive, install testdisk and attempt to recover what you can.
testdisk will recover what it can ... Good luck!
Clarification: You have to turn your computer off, because you might be overwriting files as we speak. You need a second hard drive (USB/internal) to copy the data testdisk has recovered.