How could I not know about this? It’s been in Emacs since Emacs 19.31 so it’s been around for at least 26 years. In case you, too, aren’t familiar with it, Bhaskar Chowdhury has a video that explains and demonstrates it.
The TL;DR is that Webjump allows you to call your default browser and jump to any of several preconfigured Web sites directly from Emacs. Webjump comes with several sites already defined but you can, of course, add your own or otherwise edit the list. You can even specify a function to build a site’s URL for complicated situations. See the National Weather Service entry in the default list for an example of this.
I get similar functionality with bookmark+. I’ve been using it for years since I read about it on abo-abo’s blog. It allows you to set a bookmark for any Website you like. I use it to quickly open the Irreal site all the time. Of course, bookmark+ is a separate package while Webjump is built in.
If you already have bookmark+ installed and don’t need complex processing, like the National Weather Service example, I’d just stick with that. It’s quick and easy and doesn’t involve a menu. If your needs are more complex or you don’t want to install another package, Webjump is flexible and simple to use.