You can never remind people too often to backup their computers - why? - because no matter how often you remind them when the inevitable happens and their HDD dies or becomes corrupted they panic because their computer wasn't backed up and they've lost all their data.
I was just counting to myself the various ways I backup information. I think it's 4 or maybe 5 ways:
Time Machine - Since I have 2 Mac computers - iBook and MacBook - I can access the built in TM function - non-mac users can use other programs.
I back up both machines (total backups) to a 1TB FreeAgent Drive that I purchased for $270 earlier this year from Harvey Norman.
This just sits on my desktop (my actual desktop not my computer desktop ;-) ) - I do a total backup once a week (although time machine will backup hourly/daily/weekly/monthly) on both my machines.
I also do limited backups from both machines to Mozy.
I have a home account which allows me 2GB space - this is not actual 2GB but 2GB once compressed (so I discovered after doing a restore).
I use this for important documents that I don't ever want to lose.
I also use an extremely handly little piece of software/cloud computing called "Dropbox".
How this works is very snazzy. You download some software which installs a shared folder (dropbox) on your computer. Anything you put into that folder is automatically synced with your dropbox account online. You can also install a folder on another computer and have both computers syncing via the cloud.
I use this for all my work related stuff. All my documents, pictures, various other files that I need for work are in that folder. I also have other docs that I may want to access at any time. Basically if a file, or program, or picture is in that folder I can access it from any computer in the world (or even from my iTouch).
This meant that while I was in the USA for 5 weeks in Dec/Jan I was able to do school work and then access it from my school computer when I got home.
I have a folder hierarchy within the initial dropbox folder which keeps things organised.
Dropbox has a 2GB quota for the free account. As you can see I have a way to go before I hit the limit.
I also have 2 portable drives: one is my old FreeAgent Go 75GB drive that I used to use for backups (and ran out of space) - this is for my iBook for storing stuff I want to have access to but don't need every day or even every week. For my MacBook I have a Freecom Toughdrive 320GB drive I picked up at Learning@School for $180 - I'd use it for my iBook but there's a compatibility issue with it.
The Toughdrive is a beauty. I can run movies etc right from the drive without having to download them onto the HDD - and in fact, have used it plugged into the XBOX 360 and watched videos on the TV directly from the drive.
I also have an 8GB flash drive - this being the most portable of all - I carry stuff around on here that I might want to share with others at a moments notice.
And the final place I have stuff backed up - not that I'm doing this too often now - is on DVDs - I have old school photos from the last 3-4 years; games; docs etc on DVD. I'm gradually moving those onto the 1TB drive.