After realizing that you must cover up the second hole on a 3.25" floppy in order to format it as 720k, I was able to install Lotus Agenda under DOS 6.22 under VMWare under Linux. It certainly does have some interesting features, and navigating around the text-based interface feels right at home given that I still use Mutt for my email.
If you are curious to see screenshots of Lotus Agenda in action, look in this PDF documentation for Partner's Planner:
These websites have more information: