Iteration X - Iteration X allows teams to annotate and edit any live website or web app directly in Chrome.
Visualping - Visualping is the easiest to use website checker, webpage change monitoring, website change detector and website change alert software of the web. Read more about Visualping.
Brevy (beta) - Give feedback, Google-doc style, directly on your website
Distill Web Monitor - Distill is a web monitoring tool. It can monitor RSS feeds, a webpage or a part of webpage. Alerts in the form of pop-up, audio or emails can be received.
Flycode - FlyCode (YC S22) makes web apps editable without coding so companies can iterate and release products faster - helping teams edit copy, images, and links in the code so their developers don’t have to.
WebSite-Watcher - WebSite-Watcher detects website updates and highlights all changes in the text. WebSite-Watcher monitors web pages, password protected pages, disucssion forums and much more.