The National Taxpayer's Union is one of my favorite organizations. They're on the front lines of fighting to keep our taxes low and reduce the size of our bloated government. They do this mostly through raising public awareness and letter writing campaigns and public promotion of tax reductions and opposition to excessive government spending. They target pork spending, support the FairTax, oppose internet taxation and advocate for taxpayers in congress and in the courts. That's all great stuff.
Philosophically, I'm a libertarian. I believe in people being free in almost every possible way and having an absolute right to control their own property, including controlling their own money without government interference or having the government seize it for their own use. That means I'm also a minarchist, because the best way to have government not take your money is to have a government which performs only truly necessary functions which cannot be done better by private citizens, thereby keeping the size and cost of government to a minimum. I hold to the maxim "that government governs best which governs least."
There are some legitimate responsibilities of government and there are some taxes which are better than others. Government exists to do the things which individuals cannot effectively do for themselves. That includes functions like providing for the common defense of the nation, a system of law and justice and providing certain services which we all agree don't work well when privatized, like the construction of highways, bridges and other public infrastructure. When it comes to funding government, taxes which arbitrarily take from the entire population like an income tax are the worst form of taxation, while taxes or fees which target those who make the most use of government services are more desirable. The ideal would be fee-for-service government, where you only had to pay the government for those services which you use, but realistically that type of system is hard to implement. However, whenever possible, the expense of government programs should be paid directly by those who benefit from those programs in proportion to their level of usage.
Sadly, too much of the time, our government prefers to tax citizens first and throw money at problems rather than look for more equitable and more creative solutions which would be less of a burden on the population in general. The NTU's answer to this is to oppose all increases in taxation. It's an understandable reaction, but they're relentlessly unimaginative. Sometimes the righteous fight takes them in the wrong direction.