Similar to Yousendit (Yousendit.com is not affiliated to us in any way). Matamko allows your web users to send files to each other easily. This helps increase the stickiness of your website and with the ability to display ads (for e.g. Google Adsense), Matamko gives you an additional way to monetize your web traffic. Highly viral and probably a MUST-HAVE for any serious webmasters!