Looking for the best free “noise reduction” software

[SCOBAHCAN]

Hi

I am doing some stock photography and I have been recommended to quite a few noise reduction website's but I would like to find out not only which one is the best overall but also may have the following characteristics.

- is free to download and use.
- Is easy to use.
- Is reliable.

There are probably other questions I have to ask but I cannot think of them just now- so any other information would be greatly appreciated.

Thanks a lot Craig