It's safe to say that almost all of the applications I use on a daily basis are offered free of charge and many are even open source. That being said, not all free/open source apps are everything they're made out to be. Below I've listed a few applications that I've deemed worthy, and use each and every day.

Gmail takes the cake, hands down. With its innovative labels, easy to follow conversations, ever increasing storage capacity, and simple and effective search, Gmail is the superior solution.

Dropbox is a super simple file sharing, synchronizing and backup solution. With the free account you get 2GB of space, which can be increased up to 5GB if you refer others to the service. While 2GB is not nearly enough to backup my entire hard drive, it makes quick work of synchronizing files between computers. I have two computers at the office and three computers at home and with Dropbox, the same files are available instantly on all of them.

Aviary is a unique and comprehensive online suite of photo editing applications. With a similar look and feel to that of Photoshop, Aviary’s feature set is surprisingly rich. Create an image, or even a vector image, edit it and apply some effects. With their newest feature, you can take a screen grab of any website just by going to aviary.com/http://anywebsitehere.com. Makes quick work of showing off sites in portfolios, or sending to friends.

OpenOffice is an open source office suite, great for word processing, spreadsheets, presentations and more. It's capable of reading and saving files in Microsoft Office format (.doc, .xls etc.), PDF and many others.

Firefox is my web browser of choice. All of it's features and customization options through add-ons, extensions and themes, and use of web standards make Firefox a light-weight and efficient web browser.

KeePass is an excellent and secure password manager. It saves and encrypts all your user names and passwords, along with lots more meta data (ie. description, URL, expiry date); all of which can be assigned specific icons and organized into folders. There's even extensions that will integrate the application right into your web browser. For even more fun, save your KeePass file in your Dropbox and access your passwords safely from any computer or even your Dropbox web interface!