Chrome: Want to know what's behind the linked file you're about to download? Preview it first with Peek, a simple Chrome extension that works with most common downloadable files on the internet. Peek supports PDF files; Word documents; Excel spreadsheets; PowerPoint presentations; HTML5 video (WebM, MP4, Ogg); Flash video files and HTML5 audio (MP3, WAV). Just hover your mouse cursor over a link, and a preview window will pop up. You can browse inside this preview window too, scrolling PDF pages or playing a video, to ensure it's the right file.
The extension works exactly as advertised, and will help you stay secure. Sure, Chrome is sandboxed for your protection, but it can't do much if you download a malicious file to your hard drive. Peek stops that by letting you check first. If you're really paranoid, run it through VirusTotal online as well.