This question has come up a number of times and the consensus seems to be count whatever you want. Some people count all miles, some count only the distance to work and back (subtracting out extra miles if they take the long way home), and anywhere in between. I like the idea that someone else posited, which is count all miles that they would normally drive. So a recreational bike ride wouldn't count, but going to the store would, etc...

As for myself, I only count the trips to work and back (no matter which way I take). All other riding is reflected in the (XXXX total) part.

Every year, this thread seems to get an "October surprise" entrant. That is, a poster whose first entry in the thread happens to be at the top of the list with some very impressive figure. I wonder if we'll get another one this year.