Just to explain, a group of people
In light of recent events, I have had several friends ask me how to watermark and protect their photos online. Technically, any photo posted online is free game and many are archived in places like Google Images.
That said, you can protect yourself by watermarking your photos and making your copyright known. You can also code your blog to disable right and left clicking, however you need to know that you also deactivate other external links by doing so.
And ... at the end of the day ... if someone really wants to steal your image, they can take a screen shot and crop it down to the image. Granted, it will only be as big as it appears on their screen, but they have the image like they wanted.
How you can protect yourself ...
*Resize your images before you upload them to the internet -- especially if you load them directly into blogger. Images that are taken straight out of a camera are hi resolution and huge. If someone clicks on your photo, they can pull up a huge, hi resolution photo to use for their liking. I recommend resizing them to the width of the space that your blog allows. For example, mine is custom set to 550 pixels wide -- so I always resize so the longest side of the image is 550 pixels. That way, if someone clicks on your image, they are getting a small photo that can't be printed much bigger with good quality.
If you try to click on any of my more recent images, you will never be able to pull it up. This is because I load the image to flickr and then transfer part of the html code into my blog post so that just the image appears and not the ability to click back to flickr. This is one way to help protect your images.
If you do not have photo software, you can easily resize your images on Picnik -- a free online photo processing program.
*Watermarking. I do not watermark my blog photos because I think they are pro quality ... far from it. I watermark them to protect them and to make someone think twice before they try to steal them. The watermark showing copyright is right there on the image -- not to say they can't still be stolen, but you have made your mark known.
I struggle with doing this
I watermark my photos using photoshop, however Picnik has a create | text feature that allows you to apply text to your photo ... great for watermarking.
One other thing ... I recommend noting your URL within your watermark, although you will see I have not yet added that. If someone were to see that your image had clearly been stolen and was being used in a way it was not intended, sometimes a watermark of just your blog name will not allow them to find you to tell you if they so wished. Neither will just having a copyright sign on your image. A URL, however, will allow them to easily find out where the image originated and more so, whether or not it is where it belongs online.
*Copyright. Add a copyright statement to your blog. If you scroll to the bottom of my blog, you will find mine. Right there, for everyone to see and to protect what is on my blog.
Those are the biggest things you can do to protect yourself, your images and the content of your blog. Hope this helps!