Yo, I'm tapping a Box Elder tree (Acer negundo, a species of maple) in my front yard. All maples are tappable for sap, it's just the sugar maple that has the most sugar in its sap.
This is a part of my ongoing micro-urban permaculture experiment. It certainly is exciting.
Well, the days are above freezing and the nights are almost freezing, so I figure it is the perfect time to tap. I didn't have the right bit (7/16) but I had a 3/8 bit so I wiggled it around a bit in the hole to get the extra 16th of an inch. I drilled 2" into the tree, and it is about 10" in diameter. Then I squirted the hole out with tap water and bashed the tap in. I fashioned a pail out of an old gallon jug hung it on the tap. The sap was running wildly already, and I got pretty excited about doing this on a larger scale.