How can I involve other users of SO in some action? For example voting on websocket tag synonym websockets which is not a very frequent tag and it can take relatively long time to reach score of 4. Users also have to meet specific criteria (e.g. enough reputation) which reduces target group of people who can take action. Is posting a question here on meta or chat room discussion appropriate in this scenario or are there other ways to do it?
Posting a suggestion on meta that others participate in a particular action on Stack Overflow may be rejected here. Further, you won't be reaching your target audience - experts in tag X - though a few will be here, you really need a way to get people who visit Stack Overflow involved.
Unfortunately Stack Overflow is not a social networking site, and there's no easy way (by design) to start a conversation or connect with a subgroup of Stack Overflow. It seems like successful groups connect outside Stack Overflow - via other forums, websites, IRC, mailing lists, and social networking sites in order to organize action to promote their topic on Stack Overflow.
Creating a chat room would be a good place to meet, but you're just extending the primary issue of reaching out to interested users - now you have to attract them to the chat room. Once you get their attention, organizing is easier using the chatroom, but getting them there is still a problem.
I've seen a few people spend time finding high rep users in their tags and commenting on their answers asking them to participate in various actions, and that can work, but it's slow since you have to identify such users, individually comment on each one, and it's a tossup whether they are interested or not.
While I used to be steadfastly against adding social networking features to Stack Overflow, I'm slowly realizing that one significant reason to participate in a large community is connecting people together that might be able to help each other out. Not just in the micro sense of an individual question and answer, but in the macro sense - such as Jeff Atwood and Joel Spolsky connecting and creating something that perhaps would never have happened had they not connected and bounced ideas off each other.
While I'm not advocating a full-on Facebook alike, nor Facebook/LinkedIn/etc. integration, I believe there's value in nudging users into conversations.
One simple way to do this would be to create a mini chatbox out of the chatroom, creating a chatroom for each of the major tags, and when a user is logged in, show the chatbox in the sidebar that's associated with their primary tag when on the homepage, if they are interested in a set of tags, show the chatbox for the most popular tag in their interested set, and when on a question show the chatbox associated with the most popular tag that question is associated with (or the chatbox for that question if someone has started one).
This very simple integration would encourage users to actively participate in very current discussions about their favorite tag/question/etc.
Then when you find a question that needs extra attention, post a message in the chatroom for that tag and ask people to look at it.