This needs a browser that supports data URLs. FF, Opera and IE8 will support this.
Tested on FF2 and Opera 9.
This example extracts the data of a GridPanel's Store, and uses the ColumnModel to construct an XML Excel document, converts it to Base64, and loads it into a data URL in a link.
You can click the link, and "download" the grid straight into Excel.
Obviously this only works on the data in the Store - if you are using server-side paging, then perform this processing on the server. For quick and dirty conversion of a small table to Excel, this might be useful.
If the data in the Store is volatile (It gets reloaded or edited), the data URL will have to be recalculated.