I purchased the Western Digital My book 320GB, but they are available in various sizes including the one that you have stated, also if you click on the link below you will have the chance to read a few reviews on it as well has seeing the drive as well. I purchased my hard drive about a month ago from the site below, and its absolutely fantastic, whisper quiet and very fast, I can highly recommend it!
I have the above linked Seagate. Ideally you should have a backup drive 2 times what you intend to be backing up so an 80gb drive should ideally have a 160gb backup to be viable. This way you can have 2 backups. If one file is corrupted or missing or any number of problems you can easily and quickly use the 2nd most recent back up.
Love my Seagate, 150 movies stored on it for uni and 20gb of audio and thats before my laptops backups.