Errsole - Collect, store, and visualize logs with a single module
TrackJS JavaScript Error Logging - JavaScript Error Monitoring from TrackJS gives you context about what's happening in your end-users' browsers.
AirBrake - Airbrake is the leading exception reporting service, currently providing error tracking.
Bugfender - Cloud logging for your apps, not only crashes matter
Rollbar - Rollbar collects errors that happen in your application, notifies you, and analyzes them so you can debug and fix them. Ruby, Python, PHP, Node.js, JavaScript, and Flash libraries available.
Marker.io - Visual feedback and bug reporting tool for websites