HetrixTools!

Monitors your websites every 5 minutes, totally free. Get alerts by e-mail, SMS, Twitter or RSS. Add up to 50 websites. Monitors can be refreshed for an instant check with a click. Supports https and authentication with user/password.

Pingdom web site monitoring and other infrastructure for you and instantly let you know when anything goes wrong. Measure uptime, downtime, and the performance of your website as experienced by visitors.

Monitors the performance of your websites, DNS, and email servers along with blacklist monitoring. Get alerts by e-mail and SMS. Add 1 monitor for free. Plus free online network and DNS lookup tools.

PHP Server Monitor is a script that checks whether your websites and servers are up and running. It comes with a web based user interface where you can manage your services and websites, and you can manage users for each server with a mobile number and email address.

WebSite-Watcher detects website updates and highlights all changes in the text. WebSite-Watcher monitors web pages, password protected pages, discussion forums and much more.

Port Monitor is an easy and online tool that does website and server monitoring for you 24/7 every 60 seconds and sends you or your co-workers instant email/push notifications when something goes wrong.

Uptime monitor for server. Currently fully free (beta) so it is subjected to change. Allows to monitor unlimited servers and websites. With custom CNAME you can create live status pages.

"Is It Down Right Now" monitors the status of your favorite web sites and checks whether they are down or not. Check a website status easily by using the below test tool. Just enter the url and a fresh site status test will be perfomed on the domain name in real time using our online website checker tool.

NodeQuery provides a lightweight and easy to use Linux server monitoring service. Get alerts and actively monitor the performance of your servers.

PushMon is a new kind of cloud-based monitoring system. Instead of checking public facing servers on a regular basis, PushMon will wait for pings from the objects being monitored. These objects are usually batch jobs, scheduled/cron scripts, backups, or test scripts, but really are anything that has access to the internet and can call a URL on a regular basis. If PushMon does not receive the URL "ping" by the specified schedule (like every hour, or every day or even by 5:00 PM every Fri), it will send an alert (email, IM, SMS, Twitter and/or phone call). We can monitor your database backups, your cron scripts, your background tests, your internet connectivity, your batch jobs, and a lot more. We also have an advanced but easy to use scheduling feature to alert you of problems as soon as possible. »

Website & Web Application Monitoring

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.

Discover the rich features in PowerMTA that help you adopt and adapt to changing email authentication standards including support for DKIM and SPF and setup for DMARC via an automated testing tool.

With webcron you pay per request and you can choose the monitoring frequency to your linking. When your website goes down, webcron can send you either an email or a text message (SMS).