Well, the difference really is one of nomenclature and history, whatever you may like to think about it. A scientific law is one that hasn't been disproven yet. Heck, we still refer to Newton's Laws as Laws, even though they have been disproven (or superceded, if you prefer, by the more general cases involving really high speeds and/or really small masses).
Right Wing Professor has referred to the Second Law of Thermodynamics several times - this is probably the firmest law we have in science. But, at the same time as we use it as the basis of most of our work, we don't have any good theoretical underpinning for why it should be true. We accept it because no one has ever proven it false.
Theories are pretty much in the same boat. Come up with a good model, some evidence for it. If people can't prove you're wrong, it may become accepted, and will be called either a Law or a Theory. You may have some other definition for which is which, but it is not the way these terms are actually used.
Drew Garrett