A Muslim friend of mine buys his meat from his local Masjid if this helps as it guarantees that the animal is slaughtered according to Halal specifications.
A lesser reliable source is to get from Turkish shops. Hope this helps.
There is a Turkish butcher in Josefstrase (off Langestrasse) that sell all manner of Halal meat. I buy from there most times. At the end of the Nr. 7 tram line (Morgental end) there is also a Halal butcher. I buy from this one when I can't get to Josefstr, which is a bit cheaper and has more variety, but both have good quality meat.
I had tried the search thingy, but it didn't bring up anything apart from a thread to do with Ticino. Clearly my natural failings when faced with technology
If you g to the Islamisches Zentrum on Eisgasse, you'll be able to either buy directly from the Masjid or talk to someone there and make an order (they bring it from a reliable guy in Lausanne). Or, you can try the Turkish shop on Josefstrasse; I also heard he sells Halal meat but I never bought it from there.
There is also a delicious Lebanese restaurant (Al-Mukhtar) right around the Josefstrasse area (sorry don't know the exact street name), but it's really good and cheap!
There is a Halal butchery (Turkish) at Tramendstation Wollishofen, right accross from the Shamrock, and one at Hardplatz (Tramendstation of line 8), and many places and many more.
If you do the shopping tour (on the social calendar) we go into the one in Josefstrasse that everyone is mentioning. I can recommend the meat regardless of Halal or not - its really good!