RSS gives you an easy option for integrating content across websites. In particular, you can quite easily publish content stored in SharePoint lists to a public website using RSS.
For example, imagine you had a list of job vacancies in a list on a SharePoint intranet. A well customised list with a few columns (such as JobTitle, JobDescription, ContactPerson, ClosingDate, etc.) is a great way to manage job vacancies.
Now imagine you also want to publish these job vacancies on your public website which could be built in any technology. You could achieve this by building a component on the public website that connects to the SharePoint web services and retrieves the list of job vacancies. This does, however, require a fair bit of non-trivial development.
A much easier approach is to use an RSS feed. There are various free web parts out there (e.g. Syndication Generator) that will generate an RSS feed from any SharePoint list (in the next version of SharePoint, RSS feeds will be available for all lists out-of-the-box). The next step is to write a simple UI component on the public web site that traverses through the RSS feed and displays it the way you want. Click here for a guide to build an ASP.NET RSS client including a working solution. Trust me, it is easier than you think.
I personally think RSS is one of the more exciting technologies around these days. If you look at it from a possibilities over simplicity perspective, it certainly delivers extraordinary value. I will be keen to hear from you if you have done something cool with RSS.