Kitchen Sink
appEasy (free)
Uses filters to find apps by category.
Deep Search (free)
Uses keyword search for finding relevant apps.
Inforgraphics
Collection of information graphics in several categories.
Calendar & ToDo’s
TaskTask ($4.99—supports Outlook)
Collect & Organize
Evernote (free)
diigo (free)
Sharing & “The Cloud”
Dropbox (free with paid options)
SugarSync (free with paid options)
Related Reading
Dropbox-compatible Apps Makes for Efficient Workflow
62 Things You Can Do With Dropbox