Sturgeon's Law always applies: 90% of anything is crap.
This is especially true for the Internet.
Clarke's Third Law: Any sufficiently advanced technology is indistinguishable from magic. Not much of a "Murphy's Law", but it's first corollary of that is: "Any technology distinguishable from magic is insufficiently advanced."
Law of Memory and Storage Requirements (practical version): Generously estimate how much you'll need, then multiply by four.
Law of Memory and Storage Requirements (theoretical version): You Always Need More
Murphy's Law is not.
Adding manpower to a late software project makes it later.
Oh, and: All programming languages suck.