I want to be able to use some kind of images for when I put up a post to a link (story, article somewhere else on the web), but what's the rules for what images I can use? can I use an image from the source that I'm linking to? or do I have to completely use stock images?
According to the US Patent Offic (http://www.copyright.gov/fls/fl102.html):
As such if you are taking someone else's image, even if you give credit, for the purpose of making a personal or commercial blog you will likely be considered violating copyright law by many people. There is a whole argument over whether bloggers are journalists, so I think it would be better to play it safe for now. The EFF (https://www.eff.org/issues/bloggers/legal/journalists) has more info on that
Try searching for something like "[what-you-are-looking-for] creative commons". Creative Commons (http://us.creativecommons.org/) is a series of regulations people can easily apply to their work which are human readable. Once you find an image you can look up it's license easily (in many cases it will be linked to a human readably explanation) and then follow it. In most cases you will have to give attribution plus some other restriction, but you will always no matter what be able to use the image for non commercial purposes if it uses a creative commons license, and you will often be able to use it for commercial purposes. Another way to find creative commons images is with Flikr's advanced search (http://www.flickr.com/search/advanced/?q=). At the very bottom is an option to choose images with certain licenses.
Good luck, and you can always move to Panama if that doesn't work out :).
There is something called fair use. Fair use states that a derivative of a work can be used for your own work (simplified). This is why screenshots of websites are okay. But using the image as is - is not something I would advise unless it is a larger image that you can re-size. Otherwise, don't do it. Create your own image. Better yet, use text links and avoid the issue all together. It is better for SEO.