Google has been working on this for years now, but it has finally enabled the “Click-to-play” option for plugins by default in the very latest Chrome 18 releases. The feature allows users to block plugins, like Flash Player, from loading when a site requires them, until they explicitly allow it to be run.
This could be a good way of keeping safe, speeding up browsing and getting rid of annoying ads. So far, it was only available in the "flags" section.
The feature is buried rather deep in the Chrome Settings page. Note that the new feature comes along with the redesigned Settings page which has now landed in the dev channel.
In Settings, go to Under the Hood \ Advanced Settings > Content Settings > Plug-ins and you will have the option of either blocking all plugins all the time, leaving them alone or enabling them on demand.