I am very thankful for the entire GNU/Linux/Unix stack. It is an expert interface to be sure, but for the few who have to desire to use it, its appeal is great. And in addition, it is free (in both senses)!
I have to agree on Evernote, also a big one I have not seen mentioned SourceTree, probably the best DCVS client available and it's free. Netbeans with it Chrome dev tools integration is god sent for JavaScript debugging. Rally for PM, Google Hangout for meetings, Gas Mask for host file switching, nginx for a quick and dirty dev web server. Chrome dev tools and Firebug.
Evernote, Dropbox, Zite, Expensify, Yelp, Flashlight (yup), Words with Friends, Lyft, Kayak, World of Goo
Oh, and the one I built (natch): NextGuide :)
Microsoft Office, Ultraedit, xplorer2, My Life Organized, Visual Studio 2010, LinqPad, Snagit, HackerNode (most excellen HN reader for my iPhone)
On Mac OSX - Evernote, Google drive, Trello, Thunderbird, Skype, MS Office, Adobe Photoshop, Transmit, Reeder, Spotify.
Linux / Unix, Ubuntu, Vim, Sublime Text 2, IntelliJ IDEA, Terminator, Synapse, Android, Chrome and countless others.
Google Maps (including the navigation function) on my Android phone. Saved me numerous times.
Emacs. CVS (if only for pushing new version control systems to be better).