The reference management tool, Mendeley, has a both a desktop client and a web version, which can be used together. The web version allows you to easily add citations from any computer, and there is a "suggest" function that will show you similar articles to the one in your Mendeley library. The desktop version is great for editing citations, adding tags, and adding references to your paper-in-progress.
If you have a PDF of the source you'd like to save, you can drag-and-drop it into the Mendeley desktop window.
If you've installed the web importer from above, you can also use that to import/save. Do a search in Scholar.google.com and click the "Save to Mendeley" button in your browser bar. You'll see all the articles on the page in the sidebar. Choose which ones you'd like to add with a single click on the + button, and when you see the green checkmark, it's in!
Groups allow you to collaborate on a Mendeley Library with others. Mendeley offers a number of additional features which allow you to work directly on the same documents at the same time as your collaborators.