Depends on tons of factors, typically I sit around 30wpm, but if I am writing something I've already decided on, and am not having any issues at the time, I can hit somewhere around 140wpm. Any misspellings or poor grammar slow me down, however, as I have to backspace and correct. This also makes many wpm calculators unusable for me, as many of them do not allow correcting your errors. Amusingly, I don't know where the keys on the keyboard are consciously, only subconsciously, so I can type just fine without looking at the keyboard, but if I stop to think about it, suddenly I can only type gibberish. Very annoying when cleaning my keyboard and trying to figure out where the keys go to put them back.
I've often had people tell me it sounds like a machinegun when I'm typing at high speed, as I prefer the clicky-clacky keyboards from the stone age. Newer ones just aren't durable enough to survive for long.