Extension "Hebrew Calendar": https://addons.mozilla.org/en-US/firefox/addon/1379
Release also can be downloaded from hcalendar google project.
Changes:
1.0.4.72
- Issue 56: Add "Hebrew Virtual Keyboard" into "Gematria" dialog.

List of all Issues: (http://code.google.com/p/hcalendar/issues/list)