While there are no official Zotero apps for mobile devices, there are several third-party solutions.
iOS Apps
BibUp
BibUp helps you create bibliographic references by scanning books barcodes and extracts of text. The references, including the OCRed text, can be viewed on a web page and collected using the Zotero plugin for Firefox.
PaperShip
PaperShip makes it easy to to view and add to your library, read and annotate attachments, and share references. For Mac, iPhone, and iPad.
ZotPad
With ZotPad you can view and edit your library, as well as read and annotate attachments.
Android apps
Zandy
With Zandy you can view and edit your Zotero library on your Android device.
Zed Lite
View, edit, and add to your resource library on the go.
Other tools
Zotfile
ZotFile is a Zotero plugin that syncs your library with your mobile PDF reader and extracts mobile annotations into Zotero notes.
New apps
To learn about new third-party apps for Zotero, see the Zotero for Mobile documentation pages.