Give Notes calendar users the option to mark calendar entries as also being Out of Office (OOO.) Then post an entry into a central OOO calendar (Native and Web.) I have run into several organizations that labor over creating a seperate Notes database that simply shows (manually entered) OOO entries along with multiple views (OOO by Date, by person, by department,....
The group calendar was an "almost" but missed the mark on this need entirely. Should be a snap for Lotus calendar connector guru's.
This would also help organizations pull users into using a single calendar . Yes, paper based day-timers are still used.