It all depends on what kind of files you want to store. Currently I use Dropbox which I haven't had any problems with and you are able to store 2GB of stuff with the free account. Their prices are pretty reasonable if you need more space for example their price for 50GB of storage is only 9.99 a month. If you are just storing Documents or creating Documents you could look into Google Docs. I have been using that more and more since I can log into Google from any computer and get to them without the need of installing some client piece of software like you need with the others.