<p>We have a requirement to increase the functionality of a grid we are using to edit on our webapp, and our manager keeps citing Excel as the perfect example for a data grid :/ He still doesn't really get that a Spreadsheet like control doesn't exist out of the box, but I thought I'd do a bit of searching nonetheless.</p>

<p>I've found a couple of products on Google, but was wondering if anyone else has any feedback around any such controls (obviously the cheaper or <em>ahem</em> freer the better)</p>

<p><strong>EDIT</strong> We do currently have the Telerik controls, but what the 'current' requirement is, is a control that can copy and paste (e.g) 3 cells from one row and paste them on another, the row by row editing of Telerik doesn't really cut it. We are currently in competition with an 'Excel' based solution, which is always a nightmare in winning users around, who always prefer flexibility to structure</p>

Update: with Silverlight fast approaching, maybe you can use a real excel control.
Devexpress
has a powerful grid control for both web and windows. It is not free and I guess nothing really matches Excel. But once the users started using it, they wanted every app with it. Check these
videos
especially the data grouping one.