For those who enjoy and/or find it useful to study GM games:
Came across this at www.chessgames.com
GUESS-THE-MOVE: Basically, you play though one side of a GM game, trying to remember/work out/guess each move. Each round you get a score, which is accumulated as you go along. Full points for the same move the GM played, or one just as good. Partial, zero, or negative points for lesser efforts. You can either get a game allocated randomly, or choose a game from their database of about half a million.
I find it useful to use this in conjunction with the GAME COLLECTIONS feature, where various subs have gathered together the games from many of the came collection books (and also according to theme, player, tournament etc.) I've started working through the games in Seirawan's Winning Chess Brilliancies.
There are many ways you can go about this. Personally, I like to start by reading through the game and annotation, then playing through the game a few times online, then trying GUESS-THE-MOVE, then going back to the annotation, which suddenly seems to contain much more meaning. At the end of the process, I feel like i've learnt more about the game than i would just by playing through it on a board or computer, and because you get a score it is kind of fun too.
I think part of the reason for this may be that, if all the moves of the game don't stick in your memory initially, you find yourself in the game situation trying to work out what to do next. When you're playing the part of a Fischer or Kasparov etc., that can be quite challenge!
I'm not sure if you have to be a sub or not to use this - I was already a sub when i discovered it.