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:
http://yourblog.com/tag/music+apple
And if you want to see all posts tagged “music” or “apple” then:
http://yourblog.com/tag/music,apple
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.

Very interresting post! I might check out your blog very often
Well, all that you type as a URL generates a query.
So, all that is able to return a result is based upon a query you can reproduce in a template file.
As an example, I’m currently putting together a music label web site based upon Wordpress used as a CMS. In order to ease my client’s work when posting new data, each album is split into several posts so the template will format the page using some “if it has that tag + that tag, put the post there else…”. So, the query finally is something like “if(has_tag(x+y)” which I do through some WP_query and query_posts (using wordpress 2.6.x).
You can see a working live example at this location: http://www.bonesbrigaderecords.com/?cat=3 and don’t trust the URL, the whole page is based upon brand new queries through WP_query.
If you click on an album cover, it opens a new page. Each “category” of the page is a separate post.
Yours,
Kaos
Seems to work well for Tags, but not for categories!?!
Anyone have any more advice on this?
Doesn’t seem to work for you either!
For example:
http://wpguy.com/category/articles,themes
Nope, it doesn’t work for categories. Not with 2.7 and the K2 theme, at least.
I found you had to use “+” rather than “,”. For example:
http://lowgicooking.com/tag/nutmeg+apple
I’m lookoing for just this feature! But I can’t seem to find the solution.
Has anyone found an answer to question of why it doe snot work? Has it to do with the WP version, or installed plugins?
Hoping to hear from you,
Kaan