Our local paper has an open house section that is very well received, so we do an ad there.  In both MLS systems that service our area, all the social networks, our web site and blog, trulia, zillow, realtor.com, fliers and open house coming sign at the property and call the neighbors.

MLS, Zillow, Trulia, Facebook, Twitter, LinkedIn, Pinterest, emails, etc. Someone in our area made a Facebook page for Richmond VA Open Houses and we can all post our Open Houses on it for the weekend. Although the page hasn't taken off yet, I think it would with the right promotion of the page itself. 

Everywhere.

Yes we do...But we are not allowed to put our names on the Open House.

Do not want to advertise that we are female and alone waiting on anyone that comes through the door.

It is a bit scary at times..

My brokerage advertises in in the open house directory. I also make sure to put it in MLS so that it gets picked up but other IDX feeds such as redfin, zillow, etc. On my website and here on Activerain as well.

My company posts in the newspaper, I post on various websites including MLS (people tell me this is where they find it), plenty of signs, email blast and notices in the neighborhood.

Here is a link to the original challenge in 2013 and if you look in the comments, you'll see  a bunch of posts answering the question.

http://activerain.com/blogsview/3770095/crowdsourcing-the-way-to-an-amazing-open-house

Here is a link to the webinar from 2014.

http://activerain.com/open-house-ideas

Dipti nailed this one!

Online and MLS.

Aggressively in Facebook to targeted audiences

Blog posts, signs, invitations.

Online on all web portals - including Facebook Ads.

Ginger Harper how interesting! It does have sense.......I used to have many open houses, sometimes up to 4/week ( different properties and time).

I'm going to do it right now with my listing: MLS announcement, AR blog post, spreading to Google+, FB pro pages, Twitter, LI, ( with additional reminding one day before OH),  fliers for OH, posts to community announcement boards( this one is in gated community), many OH signs with information about OH +optional: fliers invitation on the door steps( if it is a first OH), email blast to realtors, etc.

I have tried all methods to make open houses work, but they just don't in my market. 

Great question.  I'm not a real estate agent and I'm sure you'll get some great input from them.  But, I have noticed a bunch of them advertise on here by writing blog posts.  Also, I believe there is a whole crowdsourcing post and webinar on that topic from a year or two ago.  You may want to do a search within AR.