Probably the best file synchronisation tools. Ideal for keeping important documents synchronised between your computers.
Free (for 2GB)
License: Free for personal use only
Dropbox is a very useful PC tool for filesharing and sending which recently made its way on to the smartphone operating system.
The 2GB version is free to use on PCs as well as the Android, iOS and Blackberry platforms, it also lets single users sync and access their own documents, on a home or office system for example, making it particularly useful for anyone that spends a lot of time on the road.
The mobile version is very similar to the PC option making it simple for current users to get going, while it is also simple enough for new users to embrace.
Existing users will get instant access to any folders they already have saved, meaning that as soon as it is downloaded it is doing its job.