Hallo from Bangalore - I thought I'd introduce myself, and tell you a little about what's happening with chapters at Wikimedia now. I've been doing formal and informal work with Wikipedia and the Wikimedia Foundation for some time now, and like you, my main motivation is that I enjoy it. There are 29 Wikimedia chapters in existence, with more than 30 others in some stage of planning. Overwhelmingly, these chapters are in developed countries, the north, and their existence mirrors the skew in editorship (and readership): overall, it's safe to say that countries with chapters are also the predominant bases of users/readers/editors of Wikipedia and sister projects.
The point, I guess, is that any kind of organised activity around Wikimedia projects results in people from that region engaging more. Chapters are one kind of organised activity, and currently, the only means of formal affiliation with the Wikimedia Foundation. To the extent that more countries from the south engage with Wikimedia, the resulting knowledge on Wikimedia gets to look more and more proportionate to the world. Currently, despite the rich variety of languages spoken in (let's say) India and South Africa, there is less than perfect representation of them on Wikipedia, not to mention less than proportionate edits from English speakers in India and South Africa on pages relating to any topic on Wikipedia.
The opportunity then, is to write oneself in to the world in any language, including English, and also contribute beyond geographically topical subjects.
In terms of activities that the proposed South African Wikimedia chapter (and indeed any member of the Wikimedia community from South Africa) can engage in, the possibilities are literally limitless. Wikimedia Commons is a repository that can be contributed to by photographing significant aspects of South African life; subjects close to heart (South African or otherwise) can be combed and improved by university professors and students; aspects of popular culture can be explored in the many official South African languages; dictionaries of South African languages can be built; etc. etc. There are many good places to connect to what others have done, and being in a chapter provides some access to these initiatives. Foundation-l (https://lists.wikimedia.org/mailman/listinfo/foundation-l) is another good place to look; especially the archives.
I really look forward to meeting some or all of you in August and before - and the chapters committee, who will send representation to the meeting, is equally excited about helping this process. Nhlanhla Mabaso from Wits, a leader in the free software and free culture movements has many ideas to share with you, and the TACP (http://www.africancommons.org/) has wide experience in the area, and could be a valuable ally as Wikimedia South Africa goes forward.
Warm wishes, Achal