Here is my website it's an integration of two wordpress installs and phpbb forum which allows for one login to access all the installations:
Fishing the Coast
The classipress installation can be found here:
fishing the coast gear
Integration between phpbb and wordpress is achieved using wp
-united (note that this plugin is currently not overly active and only works up to wordpress 3.05 - I haven't tested in 3.1 yet). wp
-united is a phpbb plugin and uses phpbb to handle the wordpress registration and people joining. This can be seen as an issue however it seems fairly robust.
The reason I have used two installations of wordpress is so that one installation can handle the classipress and the other the rest of the website (news blogs etc etc).
Once the wp
-united integration was created between the main wordpress installation and phpbb, I installed the second wordpress installation to host classipress. Integration of the second wordpress install to achieve one login was achieved by integrating only the two wordpress installs. So there's no need to integrate the second wordpress install with the phpbb forum as this automatically occurs. Proper integration between the two wordpress installs is very hard to find on the web, however once learnt its fairly basic. I will be doing a full article on how to achieve this setup on my website over the next weeks once I get some free time.