Here is a list of extensions which I find useful under Chrome.
Adblock for Chrome is probably the most useful extension there is. While it does not function as well as the variants for other platforms (including Apple's Safari, which is also based on WebKit) the current version (2.x) is actually able to stop some ads from loading, whereas so far every other extension currently can only use CSS hiding, meaning they won't save you any bandwidth or page load time.
Browser Button for Adblock is an add-on for AdBlock to make using AdBlock easier, preventing you from having to visit the wrench menu frequently if you often mess with its settings. It's small and it works and what's more, it's optional.
AutoPager Chrome makes multi-page articles into single-page articles. It also works with google search results and lots of other sites. Creating new rules to make it work is non-trivial, but rules exist (and can be automatically downloaded) for many of the most popular sites on the internet, and lots of others besides.
AutoPager Browser Button is, like the AdBlock browser button, a GUI-only extension; this one adds a menu for AutoPager, again to keep you out of the wrench menu.
RSS Subscription Extension causes the RSS icon to pop up in the "omnibar" (aka address bar) when there is a feed to which you can subscribe. It uses online readers only, but you can define your own.
The following is an example of some very useful User JS which I use under Chrome. Using google to find other examples is usually fairly easy, although the smartest thing is probably to simply browse userscripts.org since its install button actually works in Chrome, unlike some sites with bad MIME types.
Slashdot - Remove Title Prefix does as it implies and makes the name of Slashdot stories actually appear in the tab instead of just saying "Slashdot..." Competently designed websites don't need such things. Slashdot is not one of those.
slashdot slashboxes remover removes the slashboxes from the right side of the page. This includes sidebar advertisements. Because Slashcode is so primitive and the users apparently so irrelevant you can't turn off the sidebar even if you have sufficient "karma" to hide advertisements. On my EEE 701 with its 800x480 display this results in a basically unusable site. Removing the sidebar entirely provides sufficient column width to actually read. I don't use this on my desktop system, but I mention it here since I do use it regularly and it illustrates the power of userjs for the average user.
There are many additional examples of Extensions. To get more, visit Google Chrome Extensions. This link exists inside of Chrome, but users of Chromium have a link to a different site that at least for me failed utterly. It wouldn't even install extensions, and it further lacks the variety of the official site.