Just real quick...

Because in the last post, the question was raised, I thought I would do some research and explain why Washington D.C. does not have Representatives or Senators in the U.S. Congress.
The answer lies in one of my favorite documents, the United States Constitution, Amendment 14 Section 2, and Amendment 17. I will paraphrase for your convenience. "The U.S. Senate/House shall be composed of Senators/Reprasentatives elected by each state."
The reason the District of Columbia cannot be represented in either the House or Senate is because the District of Columbia is not a state. If Districts could be represented, Congress would have the power to create districts wherever they please. This would cause increased turmoil because it would decrease the power of the states in federal government and increase the power of the controlling party of congress (because they could bolster their power by creating districts that would elect more democrat or republican representatives or senators).
This is why Washington D.C does not have representation. I do not condone the "taxation without representation" of these people. Unfortunately, "The Congress shall have power to lay and collect taxes on incomes, from whatever source derived, without apportionment among the several States, and without regard to any census or enumeration." This gives congress free reign on taxes.
Another interesting part of our constitution regarding D.C. is found in the 23rd Amendment: "The District constituting the seat of Government of the United States shall appoint in such manner as Congress may direct:

A number of electors of President and Vice President equal to the whole number of Senators and Representatives in Congress to which the District would be entitled if it were a State, but in no event more than the least populous State; they shall be in addition to those appointed by the States, but they shall be considered, for the purposes of the election of President and Vice President, to be electors appointed by a State; and they shall meet in the District and perform such duties as provided by the twelfth article of amendment"
Say what you will about what is right or wrong regarding the lack of representation for D.C., but I think that President Bush and the Congress has done the right thing by not granting D.C. voting rights because it is not constitutional.