Dropbox and Evernote are the best apps! They have done more for my personal productivity! They help me store the important things in my work, remember everything and become more organized. See links below for more reviews about these 2 apps.

Dropbox - http://www.appfavour.com/productivity/dropbox_327630330/
Evernote - http://www.appfavour.com/productivity/evernote_406056744/