Reports of the past improvements to the spamblock plugin have been very positive. On top of that, I got aware that the WordPress Akismet.com Antispam Service is available for other systems of that. So I sat down and implemented their pretty easy API into Serendipity's Spamblock plugin.
For Akismet to work, you need a Wordpress.com user account, with which you get a "API Key". You must enter this API key into the s9y spamblock plugin configuration screen, and then also set the option on how to treat Akismet marked spam (either reject or moderate).
Please try out this plugin and give us feedback. You can download the updated version here:
serendipity_event_spamblock.php and lang_en.inc.php. Put those two files into your plugins/serendipity_event_spamblock/ directory. The plugin should be compatible with Serendipity 0.9.1, 1.0-beta and 1.1-alpha.
Thanks to the guys from Akismet for offering a freely available API to check Spam against! Letting the development community fight spam with bundled efforts is the only way we might get rid of the annoying destroyers of the Web.