group and user report for a particular OU

I need to produce a report, txt or preferably xls that lists all the groups in the Bizmark OU and all of the members of those groups, filtering out computer accounts.  also, i'd like to list the firstname lastname instead of logon name; all logon names are by empoyee ID and are non intuitive.

I'd like teh report to look something like this.

sales
  Burt Blylevin
  Luke Longley
  Jeb Springfield
marketing
 paul allen
 charles zesterhaus

etc.