<p>What are some of the better AJAX Treeviews out there that support asynchronous JSON loading.</p>

<p>YUI TreeView seems nice, but bloated with tables, etc.</p>

jQuery TreeView plugin
it's really good and it haves very nice
asynchronous
JSON
loading capabilities...
ExtJS TreeView Component
, also great, multi-level asynchronous loading, excelent for large trees.