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xPressMe is a module that integrates Wordpress with XOOPS. It is being used successfully with 2.5.6. Even if you have a semi-recent version, you can automatically update both the module and Wordpress within the modules admin interface. You can use Wordpress themes or XOOPS standard theme (so it looks lie the rest of your XOOPS site) with this so it is flexible.
Mamba or Cesag might be able to point you to the most recent download URL in the SVN, I searched and only came up with OOOOLD releases.