A new feature in MediaWiki 1.4 is Patrolled edits. After clicking 'diff' on a change in Special:Recentchanges, you may see a link at the bottom, similar to the one below. Patrolled edits are restricted to administrators in most Mediawiki projects.
Patrolling edits is a way to indicate that the edit is beneficial, and to aid collaboration on filtering spam and vandalism. In the recent changes list, if you see an article which is good, you can mark it as "patrolled" so that other users know that it is good and do not necessarily have to re-check it.
Policies may vary among projects whether an article can be marked as patrolled if it is not obvious vandalism, or only when the correctness has been verified. For example, the English Wikipedia has recently implemented a different system of patrolling new pages and not each individual edit. See this page for more information.
In the Recent Changes, an unpatrolled edit looks like this:
While a patrolled one would be like this:
Note: The “block” link is only visible when logged on to an account with sysop rights.
To enable patrolling, add this line to LocalSettings.php:
$wgUseRCPatrol = true;
Note that fresh installs of version 1.4 enable RC Patrol by default.
To enable new page patrol (implemented in 1.12), add this line to LocalSettings.php:
$wgUseNPPatrol = true;
 Restricting patrolling access to sysops
If you don't want users without Administrator access to be able to mark edits as patrolled, add the following line to LocalSettings.php:
$wgOnlySysopsCanPatrol = true;
Note that this setting was removed in version 1.6 in favor of the patrol right.