Tips on what to look for in a dslr camera for independent film?

Me and my friends want to do a independent film for fun sometime next year. We were looking at cameras online and were overwhelmed by all the different kinds and prices. We saw a $600 camera called the Nikon D3100 with 14.2MP, then we found a website about 10 Examples of Stunning DSLR Cinematography and most of the videos were shoot with the $2170 Canon EOS 5D Mark II with 21.1MP. Does film get better with more megapixels or does the gains stop at a certain point. I would be the one to buy the camera and want the best for the film. I was looking to spend between 500 to 1500, but if Canon EOS 5D Mark II is that great I would save a little more. Please, any tips on what to look for would be very appreciated.

Why not actually use a video camera? They are designed for films…

Megapixels don't matter as much with video. What you need to pay attention to is frame rates.
The 5D shoots at 24 frames per second, which is great for filmic effect but if you want to do slow motion effects then it sucks. You need a higher frame rate.
The 7D is the most popular DSLR for indie filmmakers as it shoots at 24, 30, 50, and 60 frames per second. Plus lenses for the 7D are alot cheaper.
You should set aside some budget for an audio recorder as the DSLR's have poor built in microphones. The Zoom H4N is most popular.

These are some examples of different moods, all shot with a 7D.

The only interchangeable lens camera that is designed primarily as a video camera is the Panasonic GH2, hardly cheap, but currently it is the camera of choice for Indie film makers, high bit rates and 24p for the film look out of the box.

You can use all your canon lenses on it and lots more besides including lenses designed for TV and film cameras. In fact you can use most any lens as the lens to sensor distance is so short lenses for compact 35mm (Leica) 35mm film cameras (Angenieux, probably the best film lenses ever made).

A lot is made of the large sensor on the Canon 5D, but, other than the (extremely) narrow depth of field, everything else is negative as you have to use compression to get the size of each frame down to around 2Mb for video which adds noise and artefact's, rolling shutter (jello), mud when panning and moire. Smaller sensors give a much cleaner image especially in low light. The sensor in GH2 almost exactly matches Super 35mm format for size, so you get the DOF they did.

They are hackable which means you can easily raise the bitrate, I currently use 44Mb/s and get superb detail. You can go further than this, but it eats up memory cards as video files get huge. These files look stunning when projected onto 40ft cinema screens.

Canon suffer from overheating when used as video cameras and stop working til they have cooled down, not so the GH2, there's no limit on clip length with the NTSC modes and the limit in the EEC (for licensing reasons) can be removed with the same hack.

This time next year it will be different, but currently the GH2 is by far the best for video.