More and more I am starting to think that my local computer is really the weak link in storage of my data. For this reason I've put a lot of thought into this web based file hosting thing. Here's what I've come to so far.
I use Dropbox a lot. The wonderful thing about it is that the files are actually on your local machine, so you can access them without an internet connection, which is only really important with a laptop. Some people say this is a weakness because it takes up local space, but that never bothered me and I like not relying on the network to get to the files. Whenever you change anything in any of the local files it is synced up to Dropbox so you can get to it from their very slick web page or through any other computer where you have the Dropbox client installed. No manual intervention, it just notices that the files changed and up it goes. Very cool. It also has file history so you can go back to previous versions of files and recover deleted ones.
You can get a free forever account with 2GB of storage but you can pay for more.
I've heard about Box.net but haven't use it. It doesn't have the local files that Dropbox has. Here's someone else's good comparison between the two.
Another one that I really really like is jungledisk.com. This one is my favorite because they don't actually keep your files. You go out and get an amazon s3 (simple storage service) where your data is hosted and encrypted by amazon's very cool cloud disk in the sky. Jungledisk just organizes it like a filesystem for you and provides automated backup software etc. You just buy jungledisk software once (you can try it for free) and that's it. Upgrades for life. And you pay amazon for the storage, which is pretty cheap ($0.15/GB/month).
This solution really is nice because you are trusting the 800 lbs amazon gorilla with your data, and not some random fly by night company. The jungledisk file access parts are open source so you will never not be able to get your data.
So I like Dropbox's implementation but jungledisk gives me the warm fuzzies. The amazon s3 prices are still a little steap for a full out backup solution as my 2 year old is one of the more well documented individuals ever and the pictures are piling up. Of course, I have to back it up locally with multiple disks, so maybe I'm just kidding myself with how much it really costs.