MooGrid is a grid component written upon the MooTools framework.
Although far from a plugin that replaces Excel’s “freeze panes”, MooGrid can come in handy when you need to show large tabular data.
For example, you could use MooGrid for user management and overview.
MooGrid doesn’t have a documentation yet, but it does have options: you can create fixed header, footer, and colums; resize the grid; and even create multiple grids in a single page.
The plugin supports JSON and XML data, and is cross-browser compatible.
MooGrid is a “complicated” plugin, especially in the age of snippets, but it does the job, and does it well.