Zotero is great for capturing web content, PDFs, and biblographic information about published documents. Sign up with your Carleton email address to get unlimited storage!

EverNote is great for harvesting information -- especially images -- from the web. The main drawback is full sharing with a group. Only "Premium" members can have full group editing, though free members can share "view-only" access with group members to individual notes or whole notebooks.

EndNote's strengths are in ingesting citations and documents from journal and book databases and catalogs. There are options for collecting web content, but they're not as smooth as tools created for that purpose. You can use EndNote to search databases directly, too.

You can share your citations with group members, but not the documents.

If you write in LaTex and like Zotero, you'll love BibDesk, which allows you to create bibliographies, organize your papers, plus it integrates seamlessly with LaTex, allowing you to create in-text references and reference lists in your documents. It's free and an open standard, so you don't lose your bibliography over time. Mac only.