I honestly can't think of a camera that takes reallly good pictures for around $100. I know the one i'm planning on getting is $500 and it's a Nikon 60D, takes very good pictures.
I can think of plenty of cameras that cost around $100 that take good pictures... and many of them use film!
Actually, a lot of professional photographers will carry basic point and shoot cameras around with them as their "every day" cameras and only use their good ones on a planned shoot.
Its all about the skill level of the operator. Knowing the limitations of your camera, knowing how to manipulate light, etc. A very basic and very cheep digital camera can still be a powerful tool. Unless you do understand phototgraphy (not sure what your skill level is), you are probably wasting your money with the 60D as there are a plethora of features that you will probably never use since you will never leave auto mode.
as for megapixels, after 6MP, it *doesnt* matter unless you are planning on printing prints larger than 8x10 from images that you heavily crop. on the web, images are supposed to be about 72dpi... the only thing that higher megapixels do here is make the image bigger... not better quality.... and this will have dimnishing returns as with low dpi's, you will start to see pixelation much earlier.
Mike, I suggest that you not worry about the high megapixel nonsesne. When you look for your camera, there are certain features that you must have to be able to photograph fish... high shutter speed (in the 90 - 250 millisecond range), ability to work in lower light (wide aperture), and the ability to do macro and/or to accept a macro ring. Also look for a camera that has as big an OPTICAL zoom as possible... ignore the digital zoom as all that does is crop your picture (and consequently move you to pixelation faster) instead of actually zooming.
Some other features that are useful... ability to control the (simulated) ISO, and white ballance... both auto and controllable.... actually, I personally would put the white ballance in the manditory category.
for more info on the megapixel myth, check out
The Megapixel Myth
Oh... and if you really want a DSLR camera, I would check out the Canon 20D... you can pick them up used with a lens on ebay for somewhere around $150. It is a really good camera and is underappreciated since Canon has come out with cameras with higher megapixel models. It would be more that enough for what you are wanting to do.