Approximately 108,000 km/h, plus or minus a few hundred due to imprecisions in calculating Earth's orbital speed.
What?
Oh, all right, if you want to get all relative about it... 170 km/h, or 105 mi/h, on my motorcycle, and feeling like the wind was gonna tear my head off. I may have gone faster with my dad in his old 320i many years ago, but I can't really remember, and then it wasn't me driving.
I'm not much of a speed demon - actually, fast speeds scare me a fair bit, because I'm always thinking of the physics involved in going that fast - and in stopping very suddenly should an obstacle appear. Not to mention what would happen if the vehicle were to catastrophically fail in some way. *shudder*
I am, however, addicted to acceleration. Maybe I'll stop going accelerating at 100 km/h, but if I'm in a sporty mood I'll reach that speed as fast as I possibly can. Oh yes, the primal scream of a motorcycle engine redlining puts a smile on my face that just doesn't go away...