You should talk to a tax professional, but yes I think you can just claim it under other income if it's under a certain amount. You could also claim it on a different form as business income which would give you the ability to write off business expenses as well. You might consider having someone like H&R Block do your taxes. They are usually pretty good at small businesses.
If you're in the US, check out www.irs.gov - they actually have a lot of really good information.
I don't have time to talk with a tax man =/ Is this considered a business? I checked the IRS site and I couldn't find any specifications on what makes up a small business. I am the only owner and person who works on the site. This is all to confusing =/
Apparently, you are supposed to set up a business entity at first. As web business is still a business it must be run in a legitimate form. In this case you can't avoid consulting with respective officials of your region. As far as I know what might be most appropriate for you is to set up a sole proprietorship entity and to obtain a business license, so check with your local authorities how to do it.