• The Institute of Marine Biology (IfmB) of Dr. Claus Valentin. I've worked quite often at his field station at the Isola del Giglio (Italy). Thank you Claus

• The grandious Mozilla-suite. Here you will find a very good browser (Firefox), an email-programm (Thunderbird) and a powerfull calendar (Sunbird)
• Gimp, a graphic programm (quite similar to Adobe Photoshop) 
• Blender, create 3D-images and movies, as known from movies like (Toy Story etc.). Try it out!!!!
• Openoffice, all what you need in your office

• R, a statistical package, based on the syntax of S
• Ocean Data View (ODV), a GIS-like package, optimal for marine scientist. Very easy to use!

Disclaimer: This list contains links to external websites. I cannot guarantee for their correctness and their content.