Well first let me start by saying that lighting is very much a user preference. Some hobbiests swear by one specific type of lighting and anything else is just not correct.
With that said I would like to turn your attention to a few threads on this site. http://www.aquariumadvice.com/viewtopic.php?t=12
This thread has a chart and also a link to a rather long discussion on lighting. Some of it is alot more technical than your question asks but its good to know in a general sense.
For a reef tank you should try to get between 3-5 Watts per gal
. This is a general rule of thumb. This will allow you to keep most of the low and medium light needing corals.
My personal preference is PC
(Powercompact) florecent lighting. 4 55W PC
blubs with two at 10K and two actinic would be very nice for a 55 gal
. Another option would be VHO
lighting. Due to the amount of light you need for corals using NO (Normal output) florecents would require many bulbs over your tank.