What you're looking for is a good shotgun mic. That in itself
is a generic term that means any long barreled mic. You want
a good condenser (externally powered) mic with a lobar pick
up pattern to put on your boom pole. Lobar pick up means the
mic focuses its audio pick up to a narrow area.

?URL? http://www.sennheiserusa.com/newsite/?/URL?
Sennheiser is the mic most used by professional sound recordists.
They are expensive and worth it. Check out the ME-66 and the
ME-67. The MKH60 is the best if you can afford it.

?url? http://www.audio-technica.com/?/url?
Audio-Technica is cheaper. Check out the AT835B. Its a
workable mic, a little muddy and not as directional as it
should be. The AT835ST is a good mic for the price, but
it, too, sounds a bit muddy - the vocals dont sound crisp
enough for me.

?url? http://www.rodemic.com/microphones.php?/url?
Rode mics are quite good. Check the NTG (shotgun) series.

?url? http://www.azdencorp.com/?/url?
Ive never used Azden mics. Theyre inexpensive and I dont
hear too many good things about them, but if that's all you
can afford it's MUCH better than using the camera mic.

A good mic is an investment. It will last longer than your
camera - why skimp?

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The aim of an argument or discussion should not be victory, but progress.
Joseph Joubert, essayist (1754-1824)