Couple of quick ones to welcome
OS X Mountain Lion to Hints:
If you need a temporary break from all those alerts and banners, but you don’t want to turn off notifications altogether, Hints reader
guillaumegete notes that you can pause the Notification Center with one click: Press the Option key while clicking on the Notification icon in the right end of the menu bar. This will pause the display of notifications. To reactivate them, you can either Option-click the same icon again; display notifications at the right of the screen by clicking on the Notification Center icon, then toggle the Show Alerts and Banners switch from Off to On; or just wait until tomorrow, when they’ll go back on automatically.
anonymous reader points out that, as of Safari 6 (which debuted with Mountain Lion, but is available for those still using Lion, as well), you no longer need to Control- or right-click on a bookmark in the Bookmarks Bar then fill out a dialog box in order to rename that bookmark. Now you can just click and hold the bookmark; the name will be highlighted and you can then rename it right there.