looking to pitch in Note that this page only lists what has been added in each release
At some point we should get a full list of features published. If you don't see something, mail the users@qpid.apache.org list and ask. good chance we can do it 
M4 Adds the following Features - Current release
- .NET, WCF and excel support for AMQP 0-10
- SSL added for C++ broker and all clients
- Windows port for C++ client & broker
- Solaris port for C++ client & broker
- C++ Broker
- ACL
- Active-Active clustering
- Federation, push bridges & dynamic routes
- RDMA for C++ broker & C++ client (70-80us, yes us max latency on a well setup machines)
- support for message TTL
- Queue options
- added RING/ STRICT ring
- LVQ
- Exchange options
- XQuery based XML Exchange now as plugin
- Performance work
- Management for AMQP 0-10
- QMF C updates
- QMF Agent
- QMan JMX bridge for QMF
- Alerts/ logger for QMF events
- JMSXUserId
- Java broker
- Message Priority
- bug fixes
- some prep work for AMQP 0-10
M3 This release implements the AMQP 0-9 & AMQP 0-10 protocol versions
Top level themes for this release:
- C++ broker supporting AMQP 0-10
- C++ client supporting AMQP 0-10
- Java Client support AMQP 0-9 (M2.1) and AMQP 0-10
- Python Client supporting AMQP 0-9 (M2.1) and AMQP 0-10 (in addition to older versions)
- Landed the 0-10 infra for Java Broker
- Federation static routes
- Solaris Client C++ support
- bug fixes
- QMF for C++ / Python.
JIRA for M3:
http://issues.apache.org/jira/secure/IssueNavigator.jspa?reset=true&mode=hide&sorter/order=DESC&sorter/field=priority&resolution=-1&pid=12310520&fixfor=12312117
M2.1
M2.1 is a maintainer release for the M2 code branch. The detailed breakdown of JIRA's for M2.1 can be found here:
This release implements the the AMQP 0-9 protocol version
http://issues.apache.org/jira/secure/IssueNavigator.jspa?reset=true&mode=hide&sorter/order=DESC&sorter/field=priority&resolution=-1&pid=12310520&fixfor=12312720