I subscribe to Eastern Fly Fishing and thoroughly enjoy it. I also subscribe to American Angler, Fly Tyer, Fly Rod & Reel and Fly Fisherman and would recommend any of them but different reasons. I suppose it depends on what your primary interest is. For fly tying recipes and such I'd recommend Fly Tyer and Fly Fisherman over the others. For gear I'd recommend Fly Rod & Reel over the others. For specific stream info and tips I'd recommend Eastern Fly Fishing over the others. For fishing tactics on a wide variety of waters I'd recommend American Angler over the others.
Unfortunately, not all of these are available online. Each has its own focus. Hope this helps.