Speed WordPress Plugin Reviews
Yoast regularly reviews plugins on WordPress.org, judging functionality, code quality and originality. You can find the results of these reviews below for all the plugins that support Speed, or request your own plugin review here: WordPress plugin review.
You can of course also check out the latest WordPress plugin reviews.
Use Google Libraries
This is the kind of plugin that makes me happy. It just plain works. Wise to use on many, if not all, sites.
WP Smush.it
Great plugin that should be a default install on every blog that uses images to optimize them.
