If you didn't know, every Stack Exchange site also has a mobile site which provides an altered way of viewing each site, specially designed for mobile devices. You should automatically reach the mobile site just by visiting it from a mobile device, but you can also get there manually by clicking the "mobile" link in the footer.
The official mobile sites provide all functionality (except reviews), including creating new questions and answers, voting and commenting.
If you prefer a native app over the mobile site, there are plenty of apps available based on your device. Note, however, that most apps that use the Stack Exchange API, cannot create new posts, nor vote, so in general only provide read access, and might support commenting.
Available on the Apple App Store:
Available on Google Play:
Available in the Windows Store:
- There is not currently an official Windows Phone app.
Still looking? Try browsing all the apps available at Stack Apps.