A great way to discover sites you like is to find sites that offer similar content to the ones you already know and love. Google offers a very easy way to do this.
First, type in the subject matter OR site that you'd like to find more on. I find that using an actual URL retrieves much more interesting and accurate results.
See that red arrow? It's pointing to a link for "Similar Sites". Click on that link, and you'll see a whole list of sites similar to your original query.
Now, what if you don't see that "Similar Sites" link? After all, it doesn't show up on every search result. You can use this Google search command to find similar sites as well:
This will bring back similar site search results for nearly any URL.
More nifty Google tips