Did you know that WordPress supports multiple tag queries?
Let me explain. Imagine that you want to see all the posts tagged “music” and “apple”, well it’s as easy as:
And if you want to see all posts tagged “music” or “apple” then:
The same principle applies for categories.
Note: For those of you not using “pretty” permalinks, then it would be:
http://yourblog.com/?tag=music+apple or http://yourblog.com/?tag=music,apple
The only problem with this is that there is no way (that I know of) for doing such queries except typing the url by hand.