Olympic bar for dead lifts...the most effective strength training for most sports, especially skiing. The reason being that it strengthens the core so much, especially if you consciously flex your transverses muscles while lifting. Use the same bar and weights for power cleans, the second most effective for skiing. If that takes too much space, Third would be a pull up bar, palms away works the back better. I argue that course skiing is anaerobic, so doing low rep workouts and ignoring 'cardio' workouts will leave you less winded after 6 buoys in the spring. Also, studies are starting to show that high intensity/short duration exercises are better at preventing cardiovascular events than a long drawn out medium intensity cardio workout.