Drools 5.1 has been released. The main focus for this release has been around improved consumerability for users with declarative services based on Spring, Camel and CXF integration as well as the BPMN2 implementation for Flow and an improved Rete algorithm for reduced memory consumption providing better scalability for large number of objects.

You can get full release details here:
Drools 5.1 New and Noteworthy
Download
Documentation
Drools Blog
Oryx integration for web based BPMN2 Authoring

Core
JMX Monitoring
Spring, Camel and CXF integration
Knowledge Agent Incremental Change Set Support

Expert
Differential Update (reduced memory consumption for better scalability)
Channels
Live Querries
Timers and Calendars

Flow
BPMN2 (Eclipse + Web authoring)
Pluggable Variable Persistence

Guvnor
Discussions
Inbox (to monitor changes)
Bulk Importer
Built in Selector
Working Sets
Fact Constraints
Guided editor improvements
Rule Templates
Oryx integration for web based BPMN2 editing (more details here)

Rules Fest
Don't forget about the San Jose Rules Fest Oct 2010. It's a 3 day event of talks followed by a one day Boot Camp with separate rooms for Jess, Drools&jBPM, Grind Works and Open Rules. You may attend the talks or the bootcamps or both.

The Boot Camp will spend the morning introducing the 4 Drools technologies: Expert, Fusion, Flow and Guvnor and will additionally cover what's new in Drools 5.1. We will also discuss the plans for jBPM3, jBPM4 and Drools Flow. The afternoon will be an open floor where you can get time with us core developers for any questions, mentoring or assistance that you would like.

Thanks
Drools 5.1 wouldn't have been possible without the following people:

Core:
Mark Proctor
Edson Tirelli
Kris Verlaenen
Toni Rikkola
Geoffrey De Smet
Jervis Liu

Community:
Antoine Toulm
Wolfgang Laun
Nicolas Héron
Hadrian Zbarcea
Tihomir Surdilovic
Pablo Nussembaum
Lucaz Amador
Esteban Aliverti
Diego López León
Mauricio Salatino