So I have all three whereas my friend just has two and my Mum has none but what are the differences.
Post anything. Tumblr makes it effortless to share text, photos, quotes, links, music, and videos, from your browser, phone, desktop, email, or wherever you happen to be.
Twitter on the other hand is whats called micro-blogging.
And because I suck at describing it here is a fab video that explains it.
Last but not least… Friend Feed
FriendFeed helps you discover and discuss interesting stuff that your friends and family find on the web
Friend Feed is a bit like an RSS reader in that it picks up RSS feeds from blogs but it also picks up Twitter comments and other bits and pieces.