I have 4 external hard drives...
I have a pair of 500GB Seagate External Hard drives which are attached to my desktop computer and another pair of smaller (in physical size) Western Digital Passport 500GB External Hard Drives which I use when I am traveling. External hard drives have become rather inexpensive in the U.S.
I carry the two Passport hard drives when I am traveling and my workflow has evolved to downloading from my CF card via a card reader, opening the RAW file in Adobe Bridge which I have on my Toshiba notebook computer; checking the images for glaring equipment or operator malfunctions; batch renaming the files; and then copying the RAW files to each of the Passport Hard Drives. I store the drives in separate locations. As an example, when I am flying, one drive goes into my checked on bag and one drive remains in my carry on bag. I don't need to edit any images when I travel. I would rather spend my time shooting than editing on trips.
I was in a conundrum regarding downloading images on an upcoming April 2010 trip to China because I will not be carrying my Toshiba with Adobe Bridge installed. Instead, I will be using my wife's small and not particularly powerful HP notebook since that computer is a lot lighter than the 17" Toshiba. I have decided to install the free programs which came with my Canon 40D onto my wife's computer and will use Digital Photo Pro to accomplish the above workflow.
A local Camera store (Calumet Photo) has a class in Capture One Software on January 20, 2010. The price is only $50 USD for the course which includes Capture One 5.0 Software. I plan to take this course and see if I like working with Capture One 5.0 better than with Digital Photo Pro.
I keep backups of my RAW images and of my final edited image on my desktop hard drives. I also back up my images on DVD's and I keep those DVD's over at my daughter's house.