OK, I _fully_ agree that the best place to be practicing is on the air.
However, sometimes that isn't possible for me.
I've found that Morse Runner, with QSN, QSM, LIDS, QSB, and the activity set to "2" is nice practice.
It is a contest simulator, and throws all sorts of things at you.
I used it before going back on the air and credit it for helping me ignore most QRM, and cope with folks a couple hundred hertz off frequency.
It gets you used to QSB and crashes as a normal occurance.
Initally I freaked out when anything other than "perfect" was there, but Morse Runner helped take the edges off of that.
It's free and can be downloaded herehttp://www.dxatlas.com/MorseRunner/
73 de Donald