metareddit is all about reddit.com and its many (sub-)reddits. You can explore the reddits, similar ones can be grouped using tags. Once you register, you can add tags too, and vote them up or down, depending on whether they fit the reddit.
See the help page for more information on the features.
Below is a random selection of reddits, click on one and the description appears. Add a tag or two for your fellow redditors. To get a better picture of what the reddit is about, click the [+] to see the current top five submissions.
Some reddits have custom logos, here is a random selection.