StumbleUpon is a discovery engine (a form of web search engine) that finds and recommends web content to its users. Its features allow users to discover and rate Web pages, photos, and videos that are personalized to their tastes and interests using peer-sourcing and social-networking principles.
Ask.fm is a Latvia-based social networking website where users can ask other users questions, with the option of anonymity. The site was launched on June 16, 2010. Founded as a rival to Formspring. It has since overtaken the latter in terms of worldwide traffic generated.