I'm not talking about pictures, I'm talking about what you wrote. On my main page, I describe what I do (gyotaku) first in general terms and then specifics about how I do it. I can find what I wrote (in my own words) on a few other web sites with no credit given to me. In these cases, it is the general background of gyotaku. In another case, when the person is describing the specifics of what she does, and it is almost word for word, with some minor exceptions.
For one web site, I've sent an email to the website designer asking if I talk to them or the artist about possible copyright issues. For another, I sent an email to the artist asking them to credit me or write it in their own words.
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Not necessarily. You should include a © #### [Year] Michael Reimer bug in the footer of every page. The act of posting the content doesn't copyright it. For full protection, file a form with the US Copyright Office.
But in practice, it's very hard to keep content that you've published on the web from turning up elsewhere. There's no real way to police back links. Directly copying your words without attribution may be unethical, and asking them to rewrite the copy is about all you can do, since your site isn't copyrighted. Even though it appears as if your words have been plagiarized, it would be very hard to prove without documentation on file with the copyright office.
Your best source for how to go about copyrighting your material, if it is important to you, would be the copyright office itself. You can file electronically nowadays.
Copyright for Online Works - pdf
In my opinion, registering a website, which may be by its very nature a living entity, is made very difficult by the copyright system. In order to keep copyright current, each time you change it, you have to file a separate form. In practice, that's almost impossible, if you change your site frequently. Even updating your schedule quarterly can be regarded as a change.
If you publish to the web, about the best you can hope for unless you have a lot of money to throw at the problem, is ask plagiarists to link to you, give you credit for direct lifts or rewrite it, as you've done. Your legal options are few, especially without a solid copyright, and documentation of such.