At Lewis & Clark, RefWorks, Zotero and EndNote are the three most commonly used managers. RefWorks is a web app and available anywhere you have internet access. It's easy to use and get started, but doesn't have as many features as more robust programs. It's a good choice for someone new to reference management who wants to quickly get up to speed collecting online research and creating formatted bibliographies.
Zotero is a good choice for those who need to collaborate and share references. The program runs on your computer, but with a Zotero.org account you can sync your library across devices. It's easy to create group folders and share references and tags. There's a bit of a learning curve, but once you are up and running, you'll love the automatic download of available PDFs and the ability to capture webpages and other media.