First, open Apple’s iCal application and right-click on the calendar(s) you want to subscribe to. Select “Publish” and make note (either copy/paste or use the “email” option) of the locations of your published calendar.

When the calendar is published, you’ll se a “broadcast” icon appear letting you know its available. In the “Publish…” dialog box, you may also want to select some of the options available. For example, I leave the defaults and select “Publish changes automatically” and “Publish To Do items” but do not “Publish alarms” (I don’t need to be alerted to when their appointments will occur, I just need to see them on the schedule).

Back in Lotus Notes, open your calendar and select “Show Calendars” from the navigation on the left. Use the “Add a Calendar…” feature to enter the location of your .ics feed. Give the calendar a name (can’t use hyphens for some reason) and select any custom icons or colors to make it stand out. I use the same color scheme as I’ve got set up in Apple’s iCal to keep the instant corellation of “who’s calendar is what color” straight in my head.

The new calendar will appear automatically on your Lotus Notes calendar. To toggle on/off, just use the appropriate check mark.

Pretty easy stuff and extremely handy!