Question: I would like to avoid class loader leaks due to un-removed listeners. To facilitate this i believe weak or soft references to listeners would help. Strictly the only Collection methods i need are add() and iterator().

Are there any foss libraries with a Set or List that uses Weak or Soft References. 

Any suggestions would be appreciated, otherwise i will write my own.

Answer: 
You can test Facebook applications locally if you add an entry to your hosts file which points to any subdomain of the root domain you gave Facebook. For example, if your domain is example.com, you can add entry to your hosts file pointing fbtest.example.com to localhost (127.0.0.1).

You can then test away locally without having to edit your Facebook app configuration (assuming your local server is set to serve the same content to all subdomains).

Alternatively, if it's important to have the exact domain, you can just add an entry for the root domain. It just means you won't be able to access the live site while testing.
Check the 'Desktop Apps' section of <https://developers.facebook.com/docs/authentication/>
This explains how to do authentication where there's no server involved, it's aimed at desktop apps but a browser toolbar should work in a similar way