My university's club is a Go and Chess Club, so we don't make too many Go exclusive flyers, but here's one I made. It shows the various names of go with the purpose of promoting the game in the International Center on campus.

The picture is public domain (the one from the top of the Wikipedia article) and I made the rest of the flyer myself. For copyright purposes I say that you or anyone else may use and modify and do whatever you want with this flyer to promote go and go clubs.

Sadly, the best flyer I've made for the club is our "Long Live the King" flyer promoting chess, shogi, and xiangqi. I'll have to make another go flyer soon...

Some time ago I made a few posters, this is one of them:
http://flic.kr/p/hRBi1W

Feel free to use it. Maybe it is not filled with useful data but it shows a board in a nice way I think.
The rest of the posters are in Polish, but maybe I can remake them for English.

I used Phoster app and iGoban+.

Just remember the basic rules of poster/flyer design:

1) Visual first. You want to gain attention at a glance (<1 second) not after perusal.
2) Stay as text-light as possible. Again, <1 sec. to get attention. Once you have that, you've go the viewer for about 10 more seconds. Make them count.
3) Don't forget easy contact info. Consider tear-aways or something like that so people can easily take that info with them.

Good luck!

Bruce "ConstructionPaperIst" Young

This is the front of the flyer we used for our last course (cursus is Dutch for course)



The back then has a quote by Lasker, basic info on what go is, and specifics about the course.

EDIT:

Also, we used the same image to print a poster, and then we used a nice trick, which I will illustrate here:



The dashed line in this image illustrates where we would make a cut in the poster. Then we would tape a piece of paper to the back of the poster, with tape along all edges in such a way that it created a pocket. As the image shows, we would use the pocket to hold flyers, which had a red "10% discount" circle to attract extra attention.

So here the poster attracts the attention (visual first, with little text, as BaghwanB also suggests) and those whose interest is piqued can take a flyer and read more.

We would put these up in libraries, bookshops, bars and university buildings.

Glancing at it casually, I would assume Herman's poster is an invitation to a Star Trek convention of sorts.
I was surprised to see "16/09/2010" instead of "Stardate 20100916".