I did a quick search to see if there was any discussion of them here
the first one Im playing with is dropbox an online storage app which gives you at the moment 2 gig of online storage which auto updates itself from a folder on your pc with the ability for friends to dl and alter http://www.getdropbox.com/tour#1
and the other on just for laughs is http://g.ho.st/ a online os, I'm thinking this is what google will end up like , its an alpha at the moment but very usable, only doubt I have about it is security but you get a 5 gig virtual hard drive with this one and 3 gig of mail storage for free
and this one I downloaded just now, has potential if they could get the main beeb channels on it, I'm a fan of the beeb iplayer but if everything was in one place it would be great
http://www.livestation.com/