A study published in the Journal of Strength and Conditioning Research (Lees, A., Vanrenterghem, J. and De Clercq, D. The maximal and sub-maximal vertical jump: implications for strength and conditioning. J. Strength Cond. Res. 18:787-791. 2004.) found that as effort increased on jump attempts the contribution of the hip extensor muscles increased as measured by EMG.
Another study (Young, W., Wilson, G., and Byrne, C. Relationship between strength qualities and performance in standing and run-up vertical jumps. J. Sports Med. Phys. Fitness. 39: 285-293. 1999.) came to the following conclusions regarding standing bilateral and run-up unilateral jumps,
"Therefore, it appears that speed strength in concentric muscular actions is important for performancein teh standing VJ and reactive strength is relatively more important for the run-up jump." (p. 291)
That is to say that given an adequate level of basic strength, different types of jumps rely on different physical qualities, and training of more advanced athletes should reflect this. If the jumps in a sport are bilateral and sufficient time is allowed for force development, squatting, squatting with bands or chains, Olympic lifts, and weighted/resisted jump variants would be primary training methods.
On the other hand, if a sport requires unilateral jumps with short ground contact times, progressive plyometric training would be more specific to these demands. Most sports require both. The proportion of bilateral vs. unilateral jumps and the training age of your athletes will dictate how much of each type of training is used.
Other related articles on this topic can be found on google scholar or PUBMed at http://www.ncbi.nlm.nih.gov/sites/entrez?db=PubMed