In the current communities platform, you can get information delivered to you about a topic (or topics) or from a community or application within a community (e.g. forum, blog, wiki, calendar, etc.) You can even get information based on a search string -- all this can be done through something called RSS.
RSS feeds are available for every forum, topic, blog, and wiki. Subscribing to them allows you to get up to the minute updates and easily track what you have seen on Communities. You subscribe to RSS feeds in something that is often referred to as a news reader. Some popular news readers are developed by Microsoft, Sitrion, among others. You can also add RSS feeds to applications and web pages like My Yahoo.
For more specific information on RSS see this page. [Wikipedia]
To subscribe to a community or an application within a community, simply add rss to the end of the URL. Some examples of that include:
You can also use this for custom search strings -- just start by going to Advanced Search and enter what you are looking for in the search field (this can include more than one word).
Then select the various options and parameters you want scope your search to:
Once you have those set, then click the RSS button:
Then you can use the resulting URL in your RSS reader and get new and updated content that meets your defined search criteria delivered right to your RSS news reader.