what are the ways to avoid skidding off the runway apart from thrust reversers?
Your question appears to assume that thrust reversers are an acceptable way of keeping an aircraft from sliding off a slippery runway. While this may be true in rare cases, generally speaking you would NOT want to use reverse thrust to avoid skidding off a runway as that typically would exacerbate the problem.

Consider the following scenario: you have an icy runway and a strong crosswind from the right. As you start the takeoff roll, the airplane begins drifting left. You apply right rudder to correct, and the aircraft heading moves to the right of the runway direction. If you resolve the engines thrust vector into it's components relative to the runway centerline, you have most of the thrust propelling you down the runway, a much lesser amount propelling you toward the right side of the runway.

Lets say the left drift continues in spite of the engine thrust vector driving the aircraft to the right side of the runway, and you decide to abort the takeoff using reverse thrust. Thus, the thrust vector relative to the runway centerline will slow the aircraft. However the thrust vector 90&deg; to the runway centerline will be toward the left side of the runway, which when added to your leftward drift will likely put you off the left side of the runway.

If you Google "tower air 747 crash" you'll see a number of entries concerning just such a scenario and the result. I found http://flightsafety.org/ap/ap_mar97.pdf to be the most instructive, although I do not wholly agree with the conclusions or with the narrative of what happened (a friend of mine was in the jumpseat right behind the captain, and I flew as a f.o. with that captain).

An obvious answer to your question is to never get yourself into such a serious situation. Can you wait for better conditions? Is another runway available? But if you MUST use a slippery runway for either takeoff or landing (or have already foolishly committed yourself), remember that if a runway is that slippery, it's feasible to continue down the runway in a manner that your course (the runway direction) doesn't match your heading. If the captain of the Tower Air flight had elected to do that, he might not have had the accident he did, or he might have had a much more serious accident. Tough call!