Is there much differnece in ISO between 50 and 100?

My nikon d3000's lowest iso speed is 100 and i've seen lots or really good pictures on flickr that have an iso of 100.Is there much difference between them?

Iso is just how much light the camera lets in, The higher the iso the grainer the pic.
So try and keep your iso around 100-200. Use a flash if needed light. If you need more light it turn it up to 400 but try to never go higher then that or you will get a bad grainy pic and it won't look good.

It really is down to your sensor, on your camera the lowest ISO you can use is ISO 50, so it is academic.
Generally the more noise that is applied the granier the picture becomes.

You can think of the base ISO setting as a starting point (be it 50, 100 or 200 or whatever)

Some more professional cameras have an ISO 50 setting, but they have entirely different image sensors so you really can't compare directly.

Your camera will take great pics at 100-400, 800 and 1600 might be best used only when absolutely essential.

There's a measurable difference between ISO 50 and ISO 100.It takes twice the light for ISO 50 as it does for ISO 100 to get the same exposure. ISO 50 will have less noise in the picture, but you and I probably won't notice it. ISO 100 was pretty much the standard for film cameras for sunny days, and that carries over to digital cameras, so you should get great exposure at ISO 100. You will also get excellent exposure at ISO 200, the camera default. Want to know more about ISO? Here is an explanation:
http://www.nikonusa.com/...etter-itlm