Audacity® is free, open source software for recording and editing sounds. It is available for Mac OS X, Microsoft Windows, GNU/Linux, and other operating systems.
Project Website: http://audacity.sourceforge.net
Bluefish Editor A very useful text editor which I mainly use for HTML but can be used for other languages. You can also find it in the software repository in ubuntu linux.
Eclipse (Windows, Mac OS X, Linux) Development IDE which would be good for Android Development.
FileZilla is a free FTP solution.
FreeMind is a Java based application for creating Mindmaps.
Project website: http://freemind.sourceforge.net/wiki/index.php/Main_Page
Gantt Project is a cross-platform desktop tool for project scheduling and management. It runs on Windows, Linux and MacOSX, it is free and its code is opensource.
Project website: http://www.ganttproject.biz
Gedit (Linux, Mac OS X) Gedit is a very useful text editor.
GIMP (Graphics Image Manipulation Package) is an image manipulation package that is a free alternative to Photoshop.
Project Website: http://www.gimp.org
HandBrake is an open-source, GPL-licensed, multiplatform, multithreaded video transcoder, available for MacOS X, Linux and Windows.
Open Office is an open-source office software suite for word processing, spreadsheets, presentations, graphics, databases and more.
Project Website: http://www.openoffice.org
Opera is a Multiplatform web browser.
Pidgin (Linux, Mac OS X, Windows) is an easy to use and free chat client used by millions. Connect to AIM, MSN, Yahoo, and more chat networks all at once.
Sun Virtual Box Virtual Box is a brilliant piece of software that allows you to easily run an Operating System virtually on another one. It is Windows, Mac and Linux compatible. This software will help you if you want to try a new OS without clean installing it on your system. Please note that you should have atleast the system requirements of the OS you are currently running and the Virtual OS.
TrueCrypt(Free open-source disk encryption software for Windows 7/Vista/XP, Mac OS X, and Linux).
•Creates a virtual encrypted disk within a file and mounts it as a real disk.
•Encrypts an entire partition or storage device such as USB flash drive or hard drive.
•Encrypts a partition or drive where Windows is installed (pre-boot authentication).
•Encryption is automatic, real-time (on-the-fly) and transparent.
•Parallelization and pipelining allow data to be read and written as fast as if the drive was not encrypted.
•Encryption can be hardware-accelerated on modern processors.
•Provides plausible deniability, in case an adversary forces you to reveal the password:
Hidden volume (steganography) and hidden operating system.
VLC Media Player (Great for playing everything) VLC media player is a highly portable multimedia player and multimedia framework capable of reading most audio and video formats (MPEG-2, MPEG-4, H.264, DivX, MPEG-1, mp3, ogg, aac …) as well as DVDs, Audio CDs VCDs, and various streaming protocols.
Wine (Run Windows applications on Linux, BSD, Solaris and Mac OS X) allows a user to run windows applications on other platforms.
Zipeg is a very useful archive tool for both Windows and Mac.