The first trick is to figure out what is yours. Check your agreement with the companies you did the work for. Typically, the company owns the copyright on the website content and the developer does not have the copyright on anything. If you don't have an agreement you typically won't be able to copyright anything. In the future you should have some sort of agreement and make sure it spells out what copyright material is yours. If you need any help with developing this sort of agreement or interpret your current agreement, please let me know.

As to EULAs, terms of use, and copyright protection, I would strongly recommend you work with an experienced attorney to develop these. Most people try to copy another person's or company's information only to find out when it's too late (i.e. during expensive litigation) that the information should have been specifically tailored to the needs of the company/copyright holder. I heard another attorney analogize this to performing surgery on yourself rather than consulting a doctor. Obviously, the consequences aren't as dire but I think it illustrates the point. My firm handles situations like these all the time so if you need any help or advice please let me know.

I agree with the previous post as to agreements, but assuming you did the work for yourself and do own the copyright (NOT "copywrite," by the way) you can get information on how to register on the Copyright Office website. There are special rules for computer code, so look for the guides on that topic.