Offering preliminary support for OS X 10.8 Mountain Lion, Rogue Amoeba’s Audio Hijack Pro gets bumped up to version 2.10.4 with an updated Instant On component (now version 6) that improves overall system audio capture. In fact, the Instant On component is now required for capturing audio from Safari and QuickTime Player when running Mountain Lion, as well as when snagging audio from a Fluid app. ($32 new, free update, 5.2 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.