I currently use an external hard drive with some things backed up to DVD.
Might start using SkyDrive for some things like my CV which would be useful to have away from my home PC, but still a little worried about security...
You might want to add NAS to the list, as quite a few poeple are now using that. Unless you consider HDD for NAS.
I for one have a 4x HDD NAS to where I back up my data, in addition to a large internal drive.
I have 3 HDD's in my pc, and 3 or 4 'spare ones' that I've kept from older machines, I put labels on them so I know what's what, so all my back up's are on those, if I need something I just reconnect the HDD in question
At the moment, the only thing I consider important enough to backup are my photos, which are uploaded to Flickr. I know that doesn't count as a true back up, but at least I have my photos on my PC and in one other place.
I might get a few disk outs and do some documents now and again, but I don't really have much to backup.
hard drive, of course. Cloud will never be used by myself aside from the kindle stuff amazon stores on it, and I will not buy devices without built in external storage because I will not promote having to use the cloud, when flash memory is so cheap and only getting cheaper.
I wouldn't even use the term backup anymore, it should be "copy" because there should be at least 2 others from your main copy.
Main data is on a local server RAID5, that data is stored in dropbox (paid account) which is synced to local desktop and off-site desktop in a secure office/building. Images of server are also done every Saturday and once a month image is copied to dropbox, every 2-3 months images for both local machines are made and copied to on-site USB external.
I just have a backup of my boot drive on an external HDD. Important work stuff is also backed up on another drive/cloud and pen drive.
I just use TrueImage to backup my entire boot drive. Then store the image on an external drive.