How do I create a taxonomy tag from node title I have a "Tags" vocabulary, and I would like to automatically add the node title to this vocabulary as a tag on saving the node. I have tried to use the Rules module to do this, but I can't get it to work.

Can you help me?
I wouldn't recommend you doing that, you might get crazy node title names like "hello world I love peaches" and you dont want that tag.

anyway you can do a Hook_node_insert in your custom module to add your code after creating a node, then you should use taxanomy_term_save to insert your new term.

let me know if you need more on this.