Easy YouTube lets you have control over videos on YouTube using the keyboard and it works well with screen readers. the link ishttp://icant.co.uk/easy-youtube
Application Makes It Easier to Tweet Accessible Twitter (www.checkengineusa.com/ twitter/index.html) is an application that provides web accessibility for Twitter (http://twitter.com/), a free social networking service that allows friends and families to communicate and stay in touch. Written by Dennis Lembree, founder and host of a blog and podcast on web accessibility called Web Axe, Accessible Twitter includes features such as keyboard-accessible links, large default text size and high color contrast. Twitter users can follow Accessible Twitter at http://twitter.com/ AccessibleTwitr. The application is currently in alpha stage. To share suggestions and feedback, write to accessible firstname.lastname@example.org.
Facebook Accessibility - Project:Possibility Wikihttp://projectpossibility.org/wiki/index.php?title=Facebook_Accessibility