What I Use Most Often

Not in any special order:

Ubuntu 10.04 - What my machine boots up into and where it stays (instead of Windows)
Teamviewer - Cross platform zero configuration remote access software
Chrome - Fastest browser out there, synced across my different machines
X-plane - Great flight simulator (Linux and Windows)
Picassa - Cross platform photograph organizer ($5/yr for 20 Gigs of photo storage from Google )
Zumodrive - Cross platform "cloud storage" (2G free account)
SpiderOak - Cross platform backup/sync (2G free account).
TrueCrypt - Encryption for sensitive home files and for travel.
Thunderbird - Cross platform mail client
Google Earth - Endless fascination
Google Calendar - Accessible from anywhere. It sends SMS reminders of appointments to my phone
Google Reader - My RSS reader. Not pretty. Web based
iGoogle - My home page for my browsers. Various TTD lists and widgets
Google Voice - Screen calls, web voicemail, ring multiple phones. Another Google freebie
Skype - Free PC to PC voice and video. Cheap international phone calls
Stellarium - If you ever loved astronomy
Miro - Find/download videocasts
VirtualBox - I run all my Windows stuff in a Virtual XP machine using this
Quicken - For personal accounting, Windows only :(
FlightPrep - Flight Planning software, Windows only :(
iTunes - I buy. I do not steal.
Pandora - Background music. Find new stuff
PortableApps - Many of my favorite apps, carried with me everywhere on a stick
Puppy Linux - OS on a stick and runs from RAM. Very fast and useful