ReplicateMe is a simple app that runs in your local CouchDB instance. Sites running CouchDB can add a ReplicateMe button to their pages. This takes you to this application on your local instance where you can configure (continuous vs one shot, one way vs bidirectional) and trigger replication.
It uses a cookie to store the database URL, this allows you to change the name and location of your database (but assumes a standard location of the application).
I think @jchris had the idea...