Privacy & Security
Disconnect
Disconnect is a Chrome browser add-on that specializes in finding invisible trackers and then exposing them so you can decide whether or not to shut them down.
Ghostery
This is another good tracker detector—it will let you know when it blocks a tracker and show you its source. It also tries to help you understand how blocking will or won't affect your browsing.
HTTPS Everywhere from the EFF
This one automatically configures a site to show you the HTTPS version, if supported. This can stop malicious tracking from loading since it's most often not secured, but the official site.
MyPermissions Privacy Cleaner
MyPermissions will run in the background and alert you if a website tries to get your information or files. It can also scan social media accounts to look for third parties who have access to your data.
Privacy Badger from the EFF
This one analyzes how you're being tracked, especially across sites. It prides itself on blocking third-party trackers that launch in the background when you launch Chrome.
VirusTotal
VirusTotal, a subsidiary of Google, is a free online service that analyzes files and URLs enabling the identification of viruses, worms, trojans and other kinds of malicious content detected by antivirus engines and website scanners.