Hi James,
I've been working on a WordPress plugin to do just that. It's in PHP, barebones at the moment, just pulling in lead information via SOAP based on cookie. It's really barebones at the moment, but I'd be glad to share the code with you (or anyone) as it exists now.
I'm doing it as a side project on the weekends, so it's growing slowly, but I'm hoping to publish it sometime before the Marketo Summit—so no promises on how perfectly it's constructed at the moment!
Best,
Edward UnthankMarketing Operations Specialist
edwardu@yesler.com
Yesler