I've been rocking Google's new web browser Chrome for the last few days and really like it. Browsing craigslist and clicking on email mailto: links I realized there isn't an obvious way to force these links to open a gmail window in Chrome. Most Windows systems will have the default mailto handler set as Outlook Express.
One option is to install the gmail notifier program. I opted instead for a quick change to the Windows filetype settings.
Note that following these instructions will cause all mailto links to open in Google Chrome, even if you are browsing in Firefox, Safari or (gasp) Internet Explorer so make sure you want to use google Chrome as your primary browser before continuing. In Firefox, you can go to Tools->Options->Applications and configure "mailto" to set Firefox to use gmail for mailto links and not the system default (thanks to Eric for the tip).
In any windows explorer window (except desktop):
This should all be on one line with a space between the quotation mark after the path info and the https. My path was "C:\Documents and Settings\Brendan\Local Settings\Application Data\Google\Chrome\Application\chrome.exe" To find yours, just right click on a google Chrome shortcut (like the one in your start menu), go to "properties" and copy the "Target" field.
Thanks to Ed H. in the comments below for these instructions
In Vista, your path will be something like "C:\Users\Brendan\AppData\Local\Google\Chrome\Application\chrome.exe " with "Brendan" being your username.
How-To Geek has great instructions on how to accomplish this in ubuntu.
Another tip from Ed H. in the comments:
If you have “Google Apps for your Domain” (i.e. you’re having Google host your domain’s email,) you can customize it for your domain by changing the URL above so that instead of “mail.google.com/mail?…” it reads “mail.google.com/a/yourdomainhere.com?…” (obviously, use the rest of the URL mentioned above after the question mark; and use your domain instead of “yourdomainhere.com”.)