Look around you. What is happening there. Do you find anything that attracts your attention and want to tell others about it?
Read the newspaper, and do you find anything specially bothering you and feel like writing about it?
Watch the TV for few minutes, and see anything is interesting you. Why not write about some topic which attracted you?
Read a book. Are you getting tempted to write about something, which you remember suddenly while reading?
Spend a while with your friends, either online or offline. You may get tempted to write about something.
These are just few ways to find a solution to overcome writer's block. There are more ways; you only have to look for them, and think about them and act upon them.