Lifehacker reader Madlin found a useful synergy between folder syncing service Dropbox and the embeded desktop calendar Rainlendar. Since they both work on all platforms, it's easy to synchronise calendars between every desktop.
If you're looking to synchronise Rainlendar with your online Google/Yahoo/Exchange calendar, you're probably out of luck, unless you've got a client that can keep a local file in sync, like Outlook. That said, if you're using Rainlendar for a particular calendar, or don't really need web access, this trick works great, with Dropbox or any service that keeps particular files updated across systems.
And it's not too complex a trick, actually. Whether you're downloading an iCalendar (.ics) file from Google/Yahoo/et al., copying an existing calendar, or creating a new one, simply place it somewhere in your My Dropbox folder. Alternately, you could synchronise a file outside Dropbox with a little symbolic link magic. However you do it, every system you install Dropbox and Rainlendar on, you've got a constantly synced calendar up and running on your desktop.
Looking for a more web-savvy solution? Try our guide to sync any desktop calendar with Google Calendar, which might just provide a work-around solution that keeps Rainlendar and Google Calendar in sync. Rainlendar itself does have, of course, a Google-syncing Pro version for 19.95 in Euros, but this handy little solution might make one of our readers' five favourite calendar apps a bit more convenient for no money. Thanks Madlin!