A binary distribution of JOpera for Eclipse is currently available. The latest version of JOpera is 2.4.1
To download and install JOpera,
simply tell Eclipse about the JOpera update site:
http://www.update.jopera.org/
JOpera 2.3.0 and above runs on Eclipse 3.3 Europa/3.4 Ganymede on Java 1.5/1.6.
JOpera 2.1.2 runs on Eclipse 3.2.1 with GEF 3.2 on Java 1.4 (not 1.5).
The new Web Monitor only supports Firefox 2.0.
Previous versions of JOpera (1.15) require Eclipse 3.1.1, also on Java 1.4.
You can access all versions of JOpera up to 2.4.0 (including the Web services feature) from the archive update site:
http://www.update.jopera.org/old/
Note: After adding the JOpera update site URL it may be necessary to close and reopen the new P2 Update Manager dialog before proceeding with the installation of JOpera on Eclipse 3.4 Ganymede. Also, the features will not be correctly categorized.
Make sure you do a full rebuild of your JOpera projects after upgrading to a new version or switching to a different version of Java.

To keep improving JOpera, we are thankful for your feedback!
It seems that the JOpera update site listed above is blocked from the great firewall of China.
Let us know if you have problems downloading JOpera.