I have heard numerous interpretations of the 144,00, although that last one was by far the funniest.
The consensus, taking several scriptures from the OT as well, is that the 144,000 are a group of end-time believers who will be able to stand strong in the midst of great troubles. It is generally believed that they come out of Israel, and may refer to Jews, Jewish Messianic believers or Christian martyrs.
It is said that they have been sealed for their purpose,thus their ability to withstand the ravages of that time and still be a witness for Christ will be supernatural.