You can download, view the API docs, and join the mailing list from the official site (solarphp.com).
The change notes are:
* Converted all __hive() calls to __solar() instead.
* Added email and initial description to Solar_Cell_Bugs columns, removed reference to Solar_Cell_Talk (should be handled by the application object, not the bugs entity)
* Converted all 'dt' (date-time) abbreviations to 'ts' (timestamp) for consistency with Solar_Sql_Entity column type naming
* Multiple changes to Solar_Sql_Entity array keys ('ent' ==> 'tbl', 'seqname' ==> 'sequence', 'valid' ==> 'validate', 'message' ==> 'feedback'
* Added Solar_Form class (aggregates element-building instructions and validation)
* Added "None.php" drivers for Solar_User_Auth and Solar_User_Role (to facilitate having no backend for those services)
There were some internal changes to the Solar_Cell classes for Bugs and Talk (the bug and comment table entities, respectively). The biggest addition is the Solar_Form class, which is kind of like HTML_QuickForm, except it's not. ;-)
I really do have to start on at least some outline documentation; YaWiki will be perfect for it when I find the time between my MBA projects and my day job.