I can't do much to help you get your data back other than recommending the common recovery tools and services (If you check the Tekzilla forum you should get some good recommendations for inexpensive recovery programs). What I can say with authority is that you didn't lose your backup drive - you lost your PRIMARY storage. If you had lost a backup drive it wouldn't be a big deal since you'd still have your primary storage intact. But from what you're saying, this drive is the only place you had this particular data stored. I'm sure you realize by now, but that is NOT an effective backup plan and you most likely will wind up losing a significant amount of data (especially if this is a hardware failure and not a software issue).
I would *highly* recommend you rethink your data storage plan and backup strategy. You really need to either use some sort of a double redundant backup solution. Here's what I do:
My main machine has a 500 GB drive. I also have an external 500 GB drive that contains videos and such. Both of these are backed up daily to one of two 1TB USB drives over my home network. Each Thursday I unplug my backup drive and take it to work. After work I bring the *other* backup drive home and plug it into the network. This gives me THREE copies of my data at any given time, and no copy will ever be more than 1 week out of sync. If I lose my primary data drives, everything is backed up to whichever backup drive is attached to the network, and the data on the backup is, at most, 4 hours old. Even if my house burned down or got robbed I'd still have my backup drive at work. The data on that drive will never be more than 1 week old since it gets swapped out every single week. The chances of me losing my primary drives AND my local backup AND my off-site backup are basically zero. So, my data is extremely secure and other than swapping drives each week, there's no work needed on my part since the backups are all automatic. You could easily do this same thing (triple redundancy) with your primary drive, a single backup drive, and a cloud-based storage system like Carbonite. It just depends on how much data you have to backup and how fast your Internet connection is (mine is too slow and I have too much data for that to be viable for me).
Good luck getting your data back. Just please, please rethink your backup solution (seems like you don't have one at all right now) so that next time you don't have to worry about recovering your data. Just restore a backup and be done.