Dropbox - Syncs important documents
Skitch - Takes and stores my screenshots
Evernote - My second brain
- Stream content around the house
CloudApp - Only recently started to use this however I still find myself using Skitch
iAlertU - If I ever need to leave my macbook pro somewhere I will switch this on
F.lux - Useful when working late at night, however sometimes can be annoying. 
App Tamer - Not sure how well this actually works, but it used to speed up my old MacBook Pro.
Transmit - Allows me to mount my S3 server and for quick FTPing
Caffeine - When I don’t want the screen to dim
LogMeIn - Access to my computer from somewhere else
Built in apps - Bluetooth, Time Machine, WiFi, Sound, Date/Time, Battery, Spotlight
(From , founder of http://7able.com)