To find out what stairs you can currently challenge someone in, first go to the Main Stairs Page, then click on "Show your stairs only" link. The ones in BOLD are ones you can make a challenge in. .
crosseyed: Yea, you got to watch the Fischer clock games - I usually never play in one that does not at least have a 1 day bonus. (Meaning you will at the least have 1 day to make your move from the time your opponent moves)
So anything with less of a bonus (like the example here of 3 hours) means if you let your last time get down too low, a game might come back to you with very little time left..... and hopefully you are on-line. :-)