BusyMac has released BusyCal 1.6.4, which lands just two days after the release of version 1.6.3. That update provided support for the Gatekeeper security feature in OS X 10.8 Mountain Lion, as well as a few minor fixes (a dock icon redraw bug on the MacBook Pro with Retina Display and a 403 error when syncing an iCloud WebDAV calendar). It also added support for the Daylite CalDAV server. Version 1.6.4 was released quickly to fix a Gatekeeper code-signing bug that caused some installation errors. ($49.99 new, free update, 6.7 MB, release notes)
Mac OS X Services in Snow Leopard
Mac OS X Services let one application supply its powers to another; for example, a Grab service helps TextEdit paste a screenshot into a document. Most users either don't know that Services exist, because they're in an obscure hierarchical menu (ApplicationName > Services), or they mostly don't use them because there are so many of them.
Snow Leopard makes it easier for the uninitiated to utilize this feature; only services appropriate to the current context appear. And in addition to the hierarchical menu, services are discoverable as custom contextual menu items - Control-click in a TextEdit document to access the Grab service, for instance.
In addition, the revamped Keyboard preference pane lets you manage services for the first time ever. You can enable and disable them, and even change their keyboard shortcuts.