I'm working on a spreadsheet like component for AgileAgenda that I might end up turning into a general-purpose flex component at some point.

It has a couple advantages over the Flex DataGrid class including:

• Focused on data entry instead of data display.
• Full keyboard navigation
• Arrow or tab keys to move between cells
• When editing a cell, arrows move cursor instead of cells
  
• "Placeholder" rows.
  
• Automatically created as they're needed.
  
• Dimmed out rows that aren't in the dataprovider until they're edited.
• Uses a IFactory to create your value objects on the fly so you get any field validation that your value object implements.
  
• Partitions
• You can partition your data for display any way you like, independent of how it's stored.
• Each partition can have different default values for fields.
• A row can be in 1 or more partitions.
• Expandable/Collapsible
• Autocompletion
• Comes standard just by specifying a list of possible values.
• Custom item renderers/editors
• Enhanced functionality if your editor implements a special interface, but that isn't required.

Soon I'll be adding:

• Full sorting of columns (without modifying the underlying data).
• Multi-cell selection and editing capabilities
• Copy/Paste multiple cells
• Clear multiple cells at once
• etc.
  

Here's a quick screen cast of what's working so far:

http://rogue-development.com/SpreadsheetDemo.swf

(Edit, changed URL of demo movie since my Jing quota is quickly approaching)