The obvious choice is living near the Uetliberg which opens up some good trails, and some serious downhill sections.

I live on the "other side" of town, Kreis 7, and therefore have access to areas including the Zollikerberg, the Dolder, Pfannenstil and the Greifensee. I have the Pfadiweg right next to my house - 30 seconds and you're far from the madding crowds and in a forest! http://www.pfadizueri.ch/medien/pfadiweg/pfadiweg.html

Another advantage of living on this side of the lake is that on Friday night you can avoid the traffic in Zurich and travel down the north side of the lake, and meet up with the motorway down past Rapperswil. Of course this is only useful if you're heading toward Chur and the graubunden area for skiing (Davos, Flims etc)