Tim Appnel alerted me to his release of a prototype javascript “widget for enhance tag input” called TagSuggest a few days ago. Then Typepad exploded and I wasn’t able to link to his posts. Now Typepad seems to be back, so here you go.
Tim explains a bit more of the genesis of his idea in a blog entry called On Tagging Interfaces and Usability.
The widget is seeded, apparently, with a dictionary of terms. You can try it out in situ at the TagSuggest 0.1 Sample page.