I use Google Reader. Why?...Because I already use Google Apps and Gmail. If you have accounts with Yahoo or other services, they likely have an RSS reader that can be easily accessible. Consolidating your websites and software to one login is nice, regardless of who it is.
RSS feeds are also nice when you setup your own customized homepage. For reasons I previously mentioned, I use iGoogle. Others may use Yahoo or Netvibes among others to do the same thing. These services allow you to customize your homepage with relevant news, your email inbox, stock quotes, funny quotes, etc. in addition to your RSS feeds. Most services also give you the option of having multiple tabs on these customized pages so you can have several screens of customization.
If students are using blogs in class, editing Google Docs, or even working on Wikis, RSS feeds a great way for teachers to have all the student information in one place.
At the bottom of this blog, rather than the RSS feed, you will see an option to subscribe to "Posts (Atom)". Atom feeds work the same way and integrate the same way RSS feeds work, it just different coding so it has a different name. You will also see a drop down menu on the right side to subscribe this blog to the reader of your choice. Try it out...