EndNote Web now has a mobile version. Login with your email and EndNote Web password.
While full EndNote Web functionality is not available via the mobile site, EndNote Web Mobile does let you search and view your references from any Web-enabled mobile device.
More about EndNote Web.
While Zotero does not have its own mobile app, yet, there are a number of third-party apps for accessing and using your Zotero library from a mobile device.
Zandy costs $3.99 and is an Android app for viewing, editng, and syncing your library
Scanner for Zotero (Android) and BibUp (IOs) allow you to add books to your library by scanning their barcodes.
Development updates are posted on the Zotero blog.
Read more about Zotero.
