Clipmarks and Google Notebook both provide ways to easily clip, store and share parts of web pages. Here are some of my initial impressions from my brief experience with both of them.
Clipmarks gives you a lot of flexibility in what you clip on a page. You can put text, images and video from separate parts of a page all together in the same clipping. There is a Firefox extension available to help you clip and manage your clips. You can attach tags and comments to clips, and select whether a clip is private or public. Clipmarks seems to be oriented towards the social network aspect of sharing the clips with others. You can search through everyones public clips, vote for clips you like, and comment on others clips. One thing I don't like is that Clipmarks only gives you a small window for viewing clips.
Google Notebook seems to be more oriented towards clipping for your own use. It does have a facility for publishing and sharing clips, but as far as I can tell you can not simply search for other people's clips... they must give you a cryptic URL to get to their clips. Google notebook does not seem to be quite as flexible in clipping separate parts of pages either... it seems that to do that you must save each part in a separate clip. Google provides a Firefox extension to help you clip and manage your clips. Unlike Clipmarks you can even use the extension to view the clip without having to open a web page. Google notebook also gives you a large area to view the clips. It works with your Google id so you can use the same id that you use with other Google services.
I am not certain which one I will end up using. For now I plan to play with both for a biit.