i'll tell you where i lurk:

google groups:

open gov jobs

https://groups.google.com/forum/#!forum/opengovjobs

civic data alliance

https://groups.google.com/forum/#!forum/civicdataalliance

uk gov data developers

https://groups.google.com/forum/#!forum/uk-government-data-developers

linked data api discuss

https://groups.google.com/forum/#!forum/linked-data-api-discuss

code for northern virginia

https://groups.google.com/forum/#!forum/nova-brigade

geo dc

https://groups.google.com/forum/#!forum/geonerds-dc

code for dc

https://groups.google.com/forum/#!forum/dc-cfa-brigade

code for fort lauderdale

https://groups.google.com/forum/#!forum/code-for-ftl

school of open

https://groups.google.com/forum/#!forum/school-of-open

okfn task force

https://groups.google.com/forum/#!forum/okfn-task-force

open data engagement

https://groups.google.com/forum/#!forum/open-data-engagement

global open data initiative

https://groups.google.com/forum/#!forum/global-open-data-initiative

open civic data

https://groups.google.com/forum/#!forum/open-civic-data

us open gov

https://groups.google.com/forum/#!forum/us-open-government

foia machine

https://groups.google.com/forum/#!forum/foia-machine

open data day

https://groups.google.com/forum/#!forum/open-data-day

your facebook group

reddit:

http://www.reddit.com/r/opendata

http://www.reddit.com/r/opendata_pt

http://www.reddit.com/r/opengov

there's more on reddit if you feel like digging

code for america lets authors post on their tumblr, you could submit a post there

medium seems to be the cool kid blog of the day, you could double down and post it there as well.

code for philly has a linkedin group

every avenue sunlight foundation and okfn offer you: there's a slew of groups and mailing lists

code for hampton roads and code for atlanta have mailing lists, i'm betting most brigades do...

not to mention github.....man there's a ton of groups there.

i know of a few flickr groups but they're most gov-related and you have to be in gov to join...so i couldn't join.

EDIT:

i also keep all of these twitter lists:

https://twitter.com/jalbertbowdenii/lists/civhax

https://twitter.com/jalbertbowdenii/lists/openglam

https://twitter.com/jalbertbowdenii/lists/dotgov

https://twitter.com/jalbertbowdenii/lists/open-acc-sci-edu-glam-kno

https://twitter.com/jalbertbowdenii/lists/open-data-journo-crypto

https://twitter.com/jalbertbowdenii/lists/open-science-stem

https://twitter.com/jalbertbowdenii/lists/data

nicar data journalists mailing list:

http://www.ire.org/resource-center/listservs/subscribe-nicar-l/

knight-mozilla open news:

http://opennews.org/