Facebook began the process of rolling out file-sharing for groups today, allowing you to share files of most types up to 25MB. This might be useful for the average Facebook user who doesn't want to leave the service to send someone a file, but there are several other services we think are much better.
If you want to share files quickly, check out Ge.tt. It allows you to send a link to the file before it even finishes uploading so you can just get the upload started and forget about it. If you want a more group-friendly service, however, Dropmark is fantastic. It has plenty of awesome collaboration features which you can learn more about here.