People developing ReactOS also usually join our IRC-channel #reactos on freenode. If you become a steady ReactOS developer, somebody will offer you SVN write access so you don't need to submit everything to bugzilla, but that will take a while...
If you think you can participate in develompent of any particular subsystem/part of Ros you should speak with Fireball on #reactos. He may designate you to some specified field. This could speed up the joining process, but do it only if you feel experienced enough.
Regards Caemyr