visitor added tags via text field in post, plugin?

I’m looking for a plugin that will ad a text field to the bottom of posts on the single page so that visitors can type in comma separated words to be set as tags for that post.

I found the plugin, tag this, which is seriously out dated and will not even activate. I also found one called community tags which is compatible with 2.7, but when I try to set it up by inserting the php in the loop it gives a parse error.

Is there an up to date plugin for this feature? Thanks all!

p.s. very similar to the tags field we use when posting here.