I use a $20 mic and a makeshift boom, lol. I wouldn't recommend my mic for high quality stuff. Supposedly the Rode Videomic is the way to go (You can get one on Amazon for $125
...) as so many professionals have said to me to get when I was in the market for a mic. But I didn't have the $150 for a brand new one, I didn't even have $50 for a mic... Heck, my first boom was a hockey stick with foam.
Here's my current boom. I didn't make it, but a friend had made it and saw that I needed a better boom. It works ok, but considering I'm usually the camera man, it's not easy to hold the boom as well, and others tend to want to always move or tap their fingers or some stupid thing to bring up movement noises anyway, even after a warning...
I've heard you can get wireless mics that plug into the 1/8in plug, but I haven't looked into them. Then you can have the mic right on the person, or in the general area and hidden somewhere without the need for boom. I'm sure they aren't cheap though.