I have lots of applications installed on my MacBook, but this is the list of software I’d install first and use most.
Adium
http://adium.im/
Chat with multi-protocol instant messaging. I really don’t need ten applications to do the job of one.
BBC iPlayer Desktop
http://www.bbc.co.uk/iplayer/install
Watch BBC TV online or offline in high quality. There’s no need to be a slave to the TV schedule.
Dropbox
https://www.dropbox.com/
Share or publish files. I use this for ease of sharing non-confidential files.
GIMP on OS X
http://gimp.lisanet.de/Website/Download.html
Convert, edit, and retouch photos and scanned documents. This version includes some useful extras.
Gutenprint
http://gimp-print.sourceforge.net/MacOSX.php
Print to any known printer. Uses the standard Apple CUPS interface but has more and better drivers than Apple.
LibreOffice
http://www.libreoffice.org/download/
Read and edit documents, spreadsheets and presentations. You can use this well as, or instead of, Microsoft Office.
Mozilla Firefox
http://www.mozilla.org/firefox/
Browse the Internet. I prefer this to Apple Safari.
Mozilla Thunderbird
http://www.mozilla.org/thunderbird/
Manage your email. I prefer this to Apple Mail.
Skype
http://www.skype.com/get-skype/
Make video and voice calls. Not everyone has Apple FaceTime.
Sophos Anti-Virus
http://www.sophos.com/en-us/products/free-tools/sophos-antivirus-for-mac-home…
Protect yourself from malware with minimum fuss. Don’t pretend that Macs are invulnerable.
YoruFukurou
https://sites.google.com/site/yorufukurou/
Talk on Twitter with a power-user’s Twitter client. This is my current favourite.
Martin Campbell 