Dropbox is the best way to back up your files and keep your files synced between multiple computers. Once installed, Dropbox creates a folder in your Documents or Home folder. Anything saved to this folder will be backed up online and can be synced to any other computers that have Dropbox installed on the same account. You can also share folders with your friends who use Dropbox. The basic account is absolutely free and gives you 2 gigabytes of storage space. It is cross platform and runs on Windows, OSX and Linux.
Avast Antivirus is the new king of free antivirus software. Free, fast and lightweight, Avast is the best option for securing your PC or laptop against viruses. I used to recommend AVG Antivirus, but their free product has slowly devolved to a bare shadow of what it once was. Avast is certainly a much more user-friendly experience.
Kino is an open-source application that allows you to mask off your screen and darken areas that may be distracting. This is useful when reading long web documents that may have other distracting elements such as adverts or links in the side bars. A great free productivity booster!
If you use a USB key with important data on it, you should probably consider using USB Safeguard. Every year there seems to be a headline about government officials leaving sensitive data on trains and in taxis. You can avoid leaking important data by using USB Safeguard to encrypt and password protect your USB keys.
ToDoo is a fully fledged task manager. This useful application lets you organise and keep track of tasks. If you find you have problems managing your workload and need a decent task manager to help you out, look no further. With ToDoo you will always know what work needs to be completed and when it’s time to put your feet up. ToDoo is cross platform and runs on Windows, OSX and Linux.