I really like the Ben Meadows vests:
http://www.benmeadows.com/search/Field+Vest/20530/
It has a place for a compass, a relaskop, a clino, pens, rangefinder, GPS, flagging tape, an increment borer, 3l of water, and most importantly, LUNCH!
I FINALLY wore out my old favorite, a canvas vest by Pack Trails of Roseburg, OR, 2 years ago after a bajillion seasons. The Bean Meadows vest was the only one I found with the pocket arrangement I wanted. I really wish I could still get the old kind, but the new one is pretty OK, too, especially if you punch three eyelets through: 2 for flagging tape, one for a Spencer.
Also, if anybody happens to know the Pack Trails folks, I would LOVE to get JUST ONE MORE VEST, any color, large. O' course, I'll buy any I can find, but so far, so not good.
EDIT: HAW! SlowP, we're wearing the same vest! I've tried 'em all, and even though the Ben Meadows construction leaves a bit to be desired, the pocket arrangement and low cost make it the current winner.