Wiki has good stuff on this.
Here is the Second Amendment:
A well regulated militia being necessary to the security of a free State, the right of the People to keep and bear arms shall not be infringed.
The Senate explicitly defeated the restriction "for the common defense" in the amendment:
The Senate returned to this amendment for a final time on September 9. A proposal to insert the words "for the common defense" next to the words "bear arms" was defeated.
And, if origional intent is important this is worhty of note:
In no particular order, early American settlers viewed the right to arms and/or the right to bear arms and/or state militias as important for one or more of these purposes:[26][27][28][29][30][31][32][33]
deterring tyrannical government;[34]
repelling invasion;
suppressing insurrection;
facilitating a natural right of self-defense;
participating in law enforcement;
enabling the people to organize a militia system.
Some prefer to focus on the "well regulated militia" part of the second amendment - this I think is a mistake in that if we expanded this right to include weapons needed for a modern militia we would allow automatic weapons, grenades, artillery and RPGs.... (what militias have in poorly regulated regions of the world). The argument that the militia of the day used a musket is I think a poor one. Rights granted in the Bill of Rights have a tendency to expand overtime as times change (when these were passed Black people were property, women could not vote, gays would be felons) - there is no reason to argue that the right to bear arms would be stagnant to a particilar technology while the broadest definition of rights is applied to other rights.
Given the amount of back / forth that went on between the House and Senate over wording I think the phrase "the right of the People to keep and bear arms shall not be infringed" is pretty clear.
More recently the USSC has ruled that this right cannot be infringed, overturing a hand gun ban in Washington DC :
the Court ruled that the Second Amendment protects an individual's right to possess a firearm, unconnected to service in a militia[1][2] and to use that arm for traditionally lawful purposes, such as self-defense within the home.
This is particularly damning to the point about militia use and any doubt about the intent to allow private ownership of arms for self-defense.
http://en.wikipedia.org/wiki/Second_Amendment_to_the_United_States_Constitution