I don't know of any good graphical tools that work well with recent jackrabbit versions. However I find the standalone CLI client quite powerful as it allows you to perform all the simple commands easily and is scriptable as well.
If you use the standalone server of jackrabbit you can connect either via davex (recommended)
java -jar jackrabbit-standalone-2.2.7.jar --cli http://localhost:8080/server
or via RMI
java -jar jackrabbit-standalone-2.2.7.jar --cli rmi://localhost:1099/rmi
E.g. creating a new node is as simple as issuing a
addnode "test"
Browsing the repository is done with the unix commands: cd, ls and in addition lsprop to list the property values.
For all commands that are available in the client run
help