1. Taxes - been here before but it's worth saying again. The rich have an enormous advantage when it comes to taking advantage of tax exemptions. Corporations (which are getting more and more like extremely wealthy people every court decision) are the most egregious example of this, with many "American" companies paying virtually no taxes as a result of complex accounting structures and multinational presences. All this made possible by complex tax codes and armies of lawyers and accountants.
2. Civil and Criminal cases - Legal fees make basically everything about the courtroom experience farcically favorable to the wealthy. This is most awful in civil suits, where discrepancies in wealth lead to major corporations being able to bully people into settling cases that, given equal means, would assuredly go to court. Recent examples: the GeoHotz fiasco, or any RIAA suit. It's also pretty bad in criminal courts, where rich people have a great deal more access to effective legal council (there are public defenders, even really good ones, but that's a mixed bag), and can much more easily avoid the painful side effects of criminal suits because they can afford bail. It's awful just how much time innocent poor people spend in prison waiting for their trial merely because they can't afford bail. Likewise, rich people suffer significantly less from tickets and other fines and penalties, so they have much less incentive to obey laws whose violation results in such penalties. All of this is before we even consider things like cronyism or bribery which are at least theoretically illegal.
3. Political Influence - I just recently was reading about a dinner party fundraiser hosted by the Obama campaign. Tickets were going for 35,800 dollars. For that price you got to eat and hobnob with the President of the United States, with only 60 other people around. While I'm sure Obama has a fairly well established set of political views, it certainly can't hurt the agendas of the dinner guests to have a chance to chat with him. If you consider the fact that all of the fund raising dinners, charity drives, and donation things that occur in the upper echelon of politics are attended more or less exclusively by people able to drop 35K on a dinner party then you can probably pretty quickly recognize why politicians might favor the agendas of the very wealthy. It's almost an accident at this point, the very wealthy are the only people they're really hanging out and chatting with; how could they be expected to favor anyone else? It get's a lot less accidental when you look at things like corporate giving and campaign donations and the like. Money buys you media time, which gives you a disproportionately large voice in the public arena. All of this rather handily explains items 1 and 2 in this list. Turns out of wealth gives you a bigger voice in the making of laws, the laws will grow in favor of you. I bet we are all surprised by this.