How much karma does one need to make a top-level post or meetup announcement? A new user wants to announce a new meetup in Kiev. If you want to help them out, you can upvote their comment.
Creating a post in Discussion only requires “a few” points of karma; creating one in Main requires 20. I believe 20 is also required for creating a Meetup post; in most ways those appear to be treated as posts to Main (for example, up- and down-votes on them count for 10x the usual amount of poster karma).
Source: The LW FAQ, specifically http://wiki.lesswrong.com/wiki/FAQ#Why_do_I_want_high_karma.3F