Share news/opinions/ideas with a group
The world wide web has enabled networks of information through the simple mechanism of the hyperlink. This means that information posted on the web can include links to other information and can be linked to from other sources. Thus the simplest way to share news/opinions/ideas with a group is to create a web page and send group members a address (or url) to your page.
Creating a web page is not the only way to share news/opinions/ideas. Here's a list of more recent technologies for sharing:
Blogs simplify the creation of web pages, by allowing you to add multiple "posts" to a single page which the blogging tool then arranges with your most recent posts first. Blogging platforms allow others to comment on your posts and for you to respond
To much work to compose a long blog post? Consider Twitter, a tool that allows you to quickly make a short post (referred to as a "tweet")
Social networking sites like Facebook allow you share news/opinions/ideas via their status update feature.