Using jsTree As TreeView Control For DotNetNuke
Synchronous method
If you need a free opensource lightweight component for hierarchy management - use jsTree. It works fine in all major browsers and fully configurable on client (just has no server side). If you have a good javascript API to load/save data from/to server - jsTree is a very suitable tool.
Here is an example of how to build a tree management control for small hierarchies. In case of small tree it is better t have it fully loaded on client together with page.