I make extensive use of Dropbox to share files between my office Pc, my MacBook Pro and my iPhone. Furthermore, you can share complete folders with your friends/co-workers! It's a great service and it gives you 2 GB of free space or you can pay for more.
The first way to gain more free space is inviting people (250 MB each person succesfully invited), so, if you don't have Dropbox yet and want to be invited by me feel free to use my Dropbox Invite: we'll both have 250 MB of additional free space!
A simple and quick way to gain up to 640 MB is to go to this page https://www.dropbox.com/free and complete the 5 steps listed there (128 MB each step).
The Beta Version of Dropbox Mac and Windows desktop applications includes Camera Upload: an easy way to put all the photos and videos from a removable media in your Dropbox. You can ger up to 3 GB of free space: you just need to dowload and install the Dropbox Beta Version and plung in your SD card or your USB device or your mobile phone: the application will prompt you to upload photos to your Dropbox folder! For every 500 MB uploaded, you will gain 500 MB of extra free space (up to 3 GB)!
Only for Windows users: autoplay feature must be enabled. To enable that follow the manual steps suggest by Microsoft: http://support.microsoft.com/kb/967715 or simply dowload and run their fix: http://go.microsoft.com/?linkid=9743275