Photoshop Express in an online photo editing application that is free, responsive with an extremely elegant interface. And there's a full screen mode as well so one gets the feel of a desktop application.
Viscosity is an online tool to help you quickly draw Modern Art Paintings using just the mouse - no artistic skills required. You can then download your "creative work" as an image and set it as a desktop wallpaper.
Planetaki is a new service that helps you read articles from different websites at one place in a format similar to river of news. This is a completely different concept from regular RSS readers like Bloglines or Google Reader.
Virustotal virus scanner does not require you to download the file attachment to your computer and it scans your file across multiple antivirus software including AVG, Nod32, McAfee, F-Prot, etc so the chances are very high that infected email attachments will not go undetected.
Wikipedia Traffic statistics is a gold mine for content creators and SEO crowd because traffic on individual Wikipedia articles is often directly proportional to the popularity of that term on the Internet.