I am using eclipse for python. 
  How do I import an existing project into eclipse in the current workspace.
Thanks
At time of writing none of the given answers worked.
This is how it's done:

Locate the directory containing the Pydev project
Delete the PyDev project files (important as Eclipse won't let you create a new project in the same location otherwise)
In Eclipse, File->New->Pydev Project
Name the project the same as your original project
For project contents, browse to location containing Pydev project
Select an interpreter
Follow rest of the menu through

Other answers using Eclipse project importing result in Pydev loosing track of packages, turning them all into folders only.
This does loose any project settings previously set, please edit this answer if it can be avoided. Hopefully Pydev devs will add project import functionality some time.
How do I import a pre-existing python project into Eclipse?