Once I realized I needed to sync my iPad to pass every tiny file to it though iTunes I was not happy. So when I learned there was a Dropbox version for it that was free I saw an opportunity. Later, I found out that there were dropbox versions available for Linux, OSX and, of course, for Windows.
A bit later, I learned that even there is an app for my trusty Nokia E71 so I can upload picture to a dropbox folder right away.
Since then I've almost stopped using a USB pendrive in favor of dropbox and till now, the server has been great.
In a nutshell dropbox is a shared folder on the web plus an app on each computer that syncs the content of your local folder with the copy held on the Internet. Any file you add or change is modified on the network storage. To put the icing on the cake there is also a web-based access to your data, so if you're visiting a friend or using a lab computer you cannot install software on, you still can access your dropbox account files.
Basic service is free (2GB storage) and there are fee-based accounts for larger data needs. If you don't have an account, you can use this link so you'll get 250MB extra storage and so will I.
Update: Today's system upgrade of my Ubuntu Karmic complained about the key of dropbox package, so it cannot be updated. Here is what you need to type to get it upgraded properly:
sudo apt-key adv --keyserver pgp.mit.edu --recv-keys 5044912E