Sharing files or folders from Dropbox on the web has got easier than before. Today, when you sign into your Dropbox account, you can notice newly added ‘share’ button when you hover your mouse pointer over a file or folder.
Dropbox on the web gets a new Share button
You can create a shared folder and invite your friends to collaborate, click on the share button and from the drop down select ‘invite people to collaborate’ (check the screenshot below), when they accept the invite, that folder will be synced to their Dropbox account. They can able to view, edit or delete files in that folder.
Sending a link: Dropbox allows to create a link to a file and lets you send it to even non-Dropboxers, "You can also share a link to a folder. People who click a share link will be able to preview the file or the contents of a folder on the Dropbox website, they can also download a copy, but they won’t be able to edit files."
To share a folder, click on the Share button and select ‘Send link’
To share a file, click on the Share button, a link to that file will be created and appear on your screen, which you can copy to your clipboard.
[Via Dropbox blog].