Most known

• del-icio.us (Recomended links)
• Flickr (My Photos)
• Facebook
• Twitter
• Google Calendar (iCal)

Others

• Orkut Social Network
• Last.fm Music
• IMDB Movies
• Digg Social News Bookmarking
• Meneame Social News Bookmarking en español
• Technorati
• LinkedIn
• Xing
• YouTube Videos
• EBay
• Amazon
• BookCrossing Share books
• Wikipedia
• SlashDot
• Open Source Food
• FriendFeed
• 11870 Restaurants & store recomendations
• Chuza
• Lareta Galician microblogging
• SlideShare
• Netvibes
• Dopplr Travel Itineraries
• Wikiloc Trail routes
• Yahoo! Profile
• Google Profile
• GitHub: Social Coding