I was a bit lax and had a year's worth of photos to back up recently. I put them all on disc and it took a whole day (due to the size of the files, our new camera makes photos of 2 or more MBs) I should do them once a month really.
Depends on your setup. If you have a 2nd hard drive for example you can copy them to there more frequently because it's easier and relatively safe. Then copy them to CD/DVD every few months just in case the PC is stolen/explodes.
There are free backup programs to do it for you though you have to set them up so they know what to copy and where to etc.
If you are copying them off to a removable disc then DVD is better than CD because you will probably get them all on one. (2,200 x 2mb photos)
If all those seperate files are a nuisance you can use winzip or similar to create a single huge zipfile that contains a copyof all your photos. You still have to put that zipfile somewhere safe of course.
I use fsync, but you have to write a one line batch file to use it so some won't see it as user friendly.
You write a line like this in the batch file and save it. fsync.exe "C:\mypics" "D:\backups\mypics"
Whenever you click it files are copied from mypics to backups\mypics only if they are new ones or changed ones. It's faster since most files will not have changed since last time and its pointless to copy them again.
Oh and it lets me copy from one computer to another over my network.
Use an external hard-drive/back up thing. Ours is called Maxtor and wasn't that expensive.
Also, I leave my photos on my chip on my camera even after I've downloaded them on to the computer, just in case. Obviously, at some point when it gets full I have to delete, but i can keep up to 600 on there, i think.
And I send kodak galleries out to people regularly and order prints from photobox, so all my favourite pics are stored "out there" somewhere on the web, so I think that even if whole house and backup goes up in flames/is flooded, at least I've still got the ones on kodak and photobox.
As I've written this, I realise that I am ridiculously precious about my photos and spend way too much time on them. I'm incredibly lax about every other possession I own and not paranoid at all, but I do like to look after my photos!