Not so long ago, in 2nd half of 2003 more precisely, the phenomena known as social bookmaking (What is it anyway) took off and continues to grow.
del.icio.us was the pioneer in this movement and was acquired by Yahoo which aggressively entered the field of social Internet activity and helped push it forward.
There are other players in this field which provide more convenience and better features along with faster access. Two better once are Simpy and Shadows.
Dautovic 