I haven't read all the replies - by my DS (now 6) was an early reader. It's hard to pinpoint when he actually read, but there were weird things like at about 18 months he had "memorized" all 23 titles of a Beatrix Potter mini library we have and could tell you what they all were (by the number listed on the spine - even without looking at them). He definitely knew all his letters and was "reading" some simple words (cat, hat, his name) by 24 months, and then by about 3.5 I'd say he was fluently reading things like "Henry and Mudge". He also has a crazy math thing going on - and that was actually what stood out to us (perhaps to the oversight of the early reading). Before age 3 he was skip counting by 20s, skip counting backwards by 3's, had memorized all the squares from 1-12 (thanks to a book that we read to him two or three times tops), and now in first grade is easily learning algebraic concepts, division, fractions, etc.
