Box.net
I bet most of you who have Gmail accounts are probably using Gmail Drive or GmailFS to utilise the immense storage space as file storage. The minor catch with that is it violates Gmail’s Terms of Service, and Google would be within its rights to delete your account, emails and files included. A new, suitably flashy alternative to that is Box.net – sign up and you’ll get 1Gb of free storage (you can upgrade, but the prices are currently in US Dollars only so that option isn’t open to me). No ads (that I’ve seen), and you can organise your files in the traditional way (folders) and ‘the Web 2.0 way’ (ie tags).
There is a desktop application that can ‘sync’ a folder on your computer with a folder on your Box.net account, which could be very useful for backup purposes if it actually worked (lots of people, myself included, are getting an http module error that I can’t remember the name of). Still promising though – and it can even be used as a file host as you can activate public sharing of files (subject to the 10Mb maximum filesize limit, you ain’t gonna get any videos on this thing), with the obligatory but rather pointless RSS feed capability.
Sure, it has its (rather annoying) flaws, but it’s the only decent service of this type that I’m aware of, and the lack of ads (they make money by selling the premium accounts I mentioned) is refreshing. So long as it doesn’t sell itself to Yahoo it should be very good indeed once these flaws are ironed out.