As always, these are not FINAL bits, but preliminary results for QE & community testing. Not for use by customers or end users. 

Update site: http://download.jboss.org/jbosstools/updates/staging/jbosstools-4.2.0.Beta3b-updatesite-core/

Target platforms: http://download.jboss.org/jbosstools/targetplatforms/jbosstoolstarget/4.40.0.Beta4

Until the above target platform site is released, you will need to add it to Eclipse to resolve dependencies at install time. 
Once released, dependencies will be found automatically from here:
* http://download.jboss.org/jbosstools/targetplatforms/jbosstoolstarget/luna/ (latest release)
* http://download.jboss.org/jbosstools/targetplatforms/jbtcentraltarget/4.40.0.Beta4/ (upcoming milestone)
* http://download.jboss.org/jbosstools/targetplatforms/jbtearlyaccesstarget/4.40.0.Beta4/ (upcoming milestone)

New + noteworthy (subject to change): 
* https://github.com/jbosstools/jbosstools-website/tree/master/documentation/whatsnew
* http://tools.jboss.org/documentation/whatsnew/

Schedule: https://issues.jboss.org/browse/JBIDE#selectedTab=com.atlassian.jira.plugin.system.project%3Aversions-panel

Additional update sites:
* http://download.jboss.org/jbosstools/updates/staging/jbosstools-4.2.0.Beta3b-updatesite-coretests/
* http://download.jboss.org/jbosstools/updates/staging/jbosstools-4.2.0.Beta3b-updatesite-hibernatetools/
* http://download.jboss.org/jbosstools/updates/staging/jbosstools-4.2.0.Beta3b-updatesite-webtools/
Build sites:
* http://download.jboss.org/jbosstools/builds/development/jbosstools-4.2.0.Beta3b-build-core/2014-07-18_16-49-06-B197/
* http://download.jboss.org/jbosstools/builds/development/jbosstools-4.2.0.Beta3b-build-coretests/2014-07-18_16-50-49-B183/
* http://download.jboss.org/jbosstools/builds/development/jbosstools-4.2.0.Beta3b-build-hibernatetools/2014-07-18_17-11-58-B135/
* http://download.jboss.org/jbosstools/builds/development/jbosstools-4.2.0.Beta3b-build-webtools/2014-07-18_17-11-58-B185/

Changes prompting this respin-b are: 
https://issues.jboss.org/issues/?jql=labels%20in%20%28%22respin-b%22%29%20and%20%28%28project%20in%20%28%22JBDS%22%29%20and%20fixversion%20in%20%28%228.0.0.Beta3%22%29%29%20or%20%28project%20in%20%28%22JBIDE%22%2C%22TOOLSDOC%22%29%20and%20fixversion%20in%20%28%224.2.0.Beta3%22%29%29%29

To compare the upcoming version of Central (${version}) against an older version, add lines similar to these your eclipse.ini file after the -vmargs line for the appropriate version & URLs:
 -Djboss.discovery.directory.url=http://download.jboss.org/jbosstools/discovery/development/4.2.0.Beta3b/jbosstools-directory.xml
 -Djboss.discovery.site.url=http://download.jboss.org/jbosstools/discovery/development/4.2.0.Beta3b/
 -Djboss.discovery.earlyaccess.site.url=http://download.jboss.org/jbosstools/discovery/development/4.2.0.Beta3b/