voice based instant messaging ?

http://heytell.com/   "Push to talk" on iPhone and Android.
It's not quite the same as the old Nextel push-to-talk, but potentially very handy.

Look up contacts by phone number or email.  Three levels of privacy - "friends only", "friends of friends", or "anybody" would be allowed to contact you.

Too bad there is no desktop version / equivalent.

Possible to enable a "geolocation" if you don't mind being located.

data everywhere, and tools

Data Day 2012 at Northeastern Univ (Huntington Ave, Boston)
http://dataday2012.eventbrite.com/

http://data.gov  <-- !
http://data.medicare.gov   <-- !!

Research tools and visualization tools for the data you find:

http://researchresources.blogspot.com/

http://radar.oreilly.com/2010/11/update-on-weave-government-dat.htm  <-- open source

Thanks, Dan!