Sorting can group the items, but you'll still get one portal row for each record, you can't set up a sub summary like entry where you get one row for each group of items.
thanks Phil, I was pretty certain I couldn't.. does grouping within a portal qualify as a 'future requested feature'?
It's up to you: http://www.filemaker.com/company/contact/feature_request.html
But if you are using FileMaker 12 or newer and you want this as a "read only" type list of groups, you might consider using a large calculation field that produces rows and columns of grouped data: FMP 12 Tip: Summary Recaps (Portal Subtotals)
And if ExecuteSQL is not an option you want to or are able to pursue, it may be possible to set up an intermediary table that has one table for each group that then links to the records shown in your example.
Make that "one record for each group".