Excellent Lists! For me, these are my favorites. I hope they help some of you find best of breed.
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The Law Guide & Law Dictionary (I'm a lawyer and a little biased. 

  )
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Quick Settings (One touch to see all important settings, toggle, change)
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Astro File Manager - Well worth the $$$ (File management internal, SD card)
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Got To Do - $ - Best organizer/get things done, sync with ToodleDo
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Phone My PC - $ - Allows you to access your home/office PCs and see the screen, manipulate and control the machines remotely. Superb.
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IMO - Multiple IM accounts. Best instant messenger for Droid software IMHO.
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Shazam - Ever wanted to know the name of the song you were hearing and wish your phone could "listen" via the microphone and tell you?
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Tapatalk - Easiest and most efficient way to view forums. Bookmark favorite subforums too. Indispensable. 
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Agenda Widget - Simply the most efficient way to show your calendar/agenda on the home screen
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Cube Music Player - You won't be able to find this so here's the link. 

 Free, rather amazing player that provides many features stock should -- for example, making use of that button on your headset to fast forward, rewind, etc.