I’ve recently gotten in touch with Chris Fries in Chicago through the Balloon_Sked mailing list for amateur near space balloon missions.  He’s not going to near space but what his setup is elegant, simple, and very low weight.  He attaches a <3oz payload to some standard aluminized mylar party balloons, and his balloons blog for themselves reporting location, images, and video through PCS-band GSM/UMTS cellphone signals.  I hope he posts a how-to on his setup.  Launches here here and here.