Airbrake!

Rollbar collects errors that happen in your application, notifies you, and analyzes them so you can debug and fix them. JavaScript, Ruby, Python, PHP, Node.js, Android, Flash, .NET, and Java libraries are available.

Graylog is an open source syslog implementation that stores your logs in Elasticsearch. It consists of a server and web interface written in Java that accepts your syslog messages via TCP or UDP (or GELF messages) and stores it in the database.

Splunk is software that provides unique visibility across your entire IT infrastructure from one place in real time. Only Splunk enables you to search, report, monitor and analyze streaming and historical data from any source. Troubleshoot application problems and investigate security incidents in minutes instead of hours or days, monitor to avoid service degradation or outages, deliver compliance at lower cost and gain new business insights from your IT data.

Bugsnag automatically detects errors in your mobile, front-end, and back-end applications, and provides your team the tools to fix things fast. Bugsnag provides clear insights on the frequency and user impact of each error, so your team can make informed prioritization decisions. Replicating and troubleshooting is easier with automatically collected diagnostic data on where and how an error occurred. Over 3,500 of the world's best engineering teams from organizations like Square, Airbnb, Shopify, and others use Bugsnag to build better software. »

Honeybadger is the modern error management service for rails

Error tracking, uptime monitoring, and performance metrics you'll love.

RapidSpike is an uptime and performance monitoring service for websites and web applications. It simplifies monitoring, alerting and reporting to support your online presence and to ensure a positive user experience. Organisations use it to identify problems, measure performance and improve capacity planning.

God mode in Production code. OverOps tells developers why code crashes and threads freeze. Server debugging doesn't have to suck.

SessionStack helps you see your web app defects through a user’s eyes.

May be the coolest cloud based error logger for .NET web applications. Based on the de-facto standard error component ELMAH, logging errors from your webserver requires nothing more than installing a NuGet package.

Errbit is a tool for collecting and managing errors from other applications. It is Airbrake (formerly known as Hoptoad) API compliant, so if you are already using Airbrake, you can just point the airbrake gem to your Errbit server.

App Enlight- provides a helpful interface to let you and your team save time spent on debugging and reproducing errors and performance problems from a production environment.