WordPress - producing a list of posts filtered by tag and then category
Right, I have finally found a relatively simple solution to this.
There's a bug in WordPress preventing a query of both category and tags working, so query_posts('cat=2&tag=bread'); wouldn't work, but a way around this is query_posts('cat=2&tag=bread+tag=bread'); which magically works.
In a tag.php template, I wanted it to pick up the tag from that archive, so I had to do this:
<?php query_posts('cat=12&tag='.$_GET['tag'].'+'.$_GET['tag']); ?>which works perfectly.
According to the Wordpress API, you can filter by tags within a call to query_posts.
Examples:
query_posts('tag=cooking');query_posts('tag=bread,baking');query_posts('tag=bread+baking+recipe');