As a follower of the very popular productivity website Lifehacker.com, today I just stumbled on one of their most recent posts. The post, titled Lifehacker Pack for Linux: Our List of the Best Linux Downloads lists and describes a number of free/open source software products that can be downloaded and installed on Linux. The post mentions that these are mostly for the Ubuntu distribution, but many of these applications have releases for other Linux distributions as well.
I personally find this list to be very useful, since it includes many applications that one would need in everyday's work/life, and many of them are not included by default with Linux. These include: web browser (Firefox, Chrome), email client (Thunderbird), office suite (OpenOffice.org), text editor (gedit), and many more. The list even provides direct links to download these applications or to directly install them in Ubuntu.